the comet s talejds/tail12b.pdf · issue the iwca was very successful and an enjoyable time was had...

BAA COMET SECTION NEWSLETTER

THE COMET’S TALENewsletter of the Comet Section of the British Astronomical Association

Volume 6, No 2 (Issue 12), 1999 October

THE SECOND INTERNATIONALWORKSHOP ON COMETARY

ASTRONOMYNew Hall, Cambridge, 1999 August 14 - 16

After months of planning andmuch hard work the participantsfor the second InternationalWorkshop on CometaryAstronomy began to assemble atNew Hall, Cambridge on theafternoon and evening of Friday,August 13th. New Hall is one ofthe more recent Cambridgecolleges and includes a centrebuilt for Japanese students as wellas accommodation for thegraduate and undergraduatestudents. It is a women’s collegeand a few participants were laterdisturbed by the night porter doinghis rounds and making sure thatall ground floor windows wereclosed. A hearty dinner wasprovided, but afterwards I had toleave to continue last minutepreparations for the morning.

On Saturday morning, Dan Greenand Jon Shanklin made a fewopening announcements. We hadnine comet discoverers presentand five continents wererepresented. The next meetingwould take place in 4 – 5 yearstime, possibly in America. Formost of the day the BritishAstronomical Association had asales desk in the entrance foyer toNew Hall, with a range of eclipsememorabilia on offer, as well ascopies of cometary publications.

Don Machholz gave the openingtalk about comet hunting. He usedto live in a light polluted site anddrove out to Lomo Prieta forcomet searching. In 1990 hemoved 180 miles to the smalltown of Colfax (pop 1000) andhas since discovered five comets.

He had searched 1000 hours since1994 without a discovery. If theEdgar Wilson award had been inoperation he would have netted anaverage of $4000 a year, thoughsome years would be morerewarding and others less. Hissearch technique is to scaneast/west and move down in themorning sky. There are threeconditions for success – you mustlook, the comet must be brightenough and you must find it first.His first three comets were closerto the sun than those previouslydiscovered by amateurs in theprevious 25 years. Type 1 cometsare 30 – 60 deg from the Sun inthe morning sky, bright, few innumber and have small q. Type 2lie in the evening sky 60 – 120deg from the Sun, are dim,common and have large q.

Most discoveries were fromJapan, USA and Australia.Southern Hemisphere observersonly discover southern declinationcomets, however northernhemisphere observers find them inboth hemispheres. There is nosignificant trend in discoverydeclination.

Continued on page 11

Contents

Comet Section contacts 2Section news 2Tales from the Past 3Professional Tales 3Review of observations 5Comet hunting notes 10IWCA Report (cont) 11Observation of 2P/Encke 17The comet of 1807 17Predictions for 2000 18

2 THE COMET’S TALE


Comet Section contacts

Director: Jonathan Shanklin, 11 City Road, CAMBRIDGE. CB1 1DP, England.Phone: (+44) (0)1223 571250 (H) or (+44) (0)1223 221400 (W)Fax: (+44) (0)1223 362616 (W)E-Mail: [email protected] or [email protected] page : http://www.ast.cam.ac.uk/~jds/

Assistant Director (Observations): Guy Hurst, 16 Westminster Close, Kempshott Rise, BASINGSTOKE, Hampshire.(and also Editor of RG22 4PP, England.The Astronomer magazine) Phone & Fax: (+44) (0)1256 471074

E-Mail: [email protected] or [email protected]

CCD Advisor: Nick James, 11 Tavistock Road, CHELMSFORD, Essex. CM1 5JL, England.Phone: (+44) (0)1245 354366E-mail: [email protected] or [email protected]

Photographic Advisor: Michael Hendrie, Overbury, 33 Lexden Road, West Bergholt, COLCHESTER,Essex, CO6 3BX, EnglandPhone: (+44) (0)1206 240021

Subscription to the Section newsletter costs £5 for two years, extended to three years for members who contribute to thework of the Section in any way. Renewals should be sent to the Director and cheques made payable to the BAA. Thosedue to renew should receive a reminder with this mailing.

Section news from the Director

Dear Section member,

As you will read elsewhere in thisissue the IWCA was verysuccessful and an enjoyable timewas had by all participants. I waspleased to see a goodrepresentation from Britishamateurs and hope that the nextworkshop, likely to be held in theUSA in five years time will see anequally large British contingent.

On September 17 I became theproud discoverer of a cometmyself. As with many discoveriesthere was an element of luck to it,in that I just happened to be thefirst person to scan the real timeimages from the SOHO LASCOcoronagraph and recognise thatthere was an intruder present. Thediscovery does however followDon Machholz's tenets of cometdiscovery: you have to look, thecomet must be bright enough andyou have to find it first.

I have agreed to take on theDirectorship of the Comet Sectionof the Society for PopularAstronomy. I've actually been amember of this society longer thanI have been a member of the BAA.SPA members will be able tosubscribe to The Comet's Tale andtheir observations will be includedin the Section archives. I look

forward to close co-operationbetween the two groups.

Since the last newsletterobservations or contributions havebeen received from the followingBAA members: Sally Beaumont,Denis Buczynski, John Fletcher,James Fraser, Maurice Gavin,Werner Hasubick, Guy Hurst,Nick James, Martin Mobberley,Bob Neville, Gabriel Oksa, RoyPanther, Jonathan Shanklin, DavidStorey, David Strange, JohnVetterlein and Alex Vincent

and also from: Jose Aguiar,Alexandr Baransky, John Bortle,Reinder Bouma, Jose Carvajal,Tim Cooper, Stephen Getliffe,Guus Gilein, Bjorn Granslo,Roberto Haver, AndreasKammerer, Heinz Kerner, AtillaKosa-Kiss, Martin Lehky,Rolando Ligustri, Andrew Pearceand Seiichi Yoshida (apologies forany errors or omissions).

Comets under observation were:10P/Tempel 2, 29P/Schwassmann-Wachmann 1, 37P/Forbes,52P/Harrington-Abell,95P/Chiron, 134P/Kowal-Vavrova, 140P/Bowell-Skiff,1995 O1 (Hale-Bopp), 1997 BA6(Spacewatch), 1998 M5(LINEAR), 1998 P1 (Williams),1998 T1 (LINEAR), 1998 U3

(P/Jager), 1998 U5 (LINEAR),1999 F2 (Dalcanton), 1999 H1(Lee), 1999 H3 (LINEAR), 1999J2 (Skiff), 1999 J3 (LINEAR),1999 K2 (Ferris), 1999 K3(LINEAR), 1999 K5 (LINEAR),1999 K6 (LINEAR), 1999 K8(LINEAR), 1999 L2 (LINEAR),1999 N2 (Lynn), 1999 S3(LINEAR), 1999 S4 (LINEAR).

Many of the fainter comets wereobserved by Seiichi Yoshida whois using a CCD camera on an 18cm reflector to very good effect.It is pleasing to have received afew CCD observations from UKobservers over the summer and Ihope the winter will bring manymore.

The observing supplementaccompanying this issue of TheComet's Tale is thinner than usualto compensate for the thicker mainsection. I have only givenephemerides for comets brighterthan 10th magnitude. Ephemeridesfor fainter comets are available onthe Section web page andobservers can generate their owncharts using the elements given inthe supplement. In future I willonly give ephemerides for faintercomets if they are particularly inneed of observation.

Jonathan Shanklin

1999 October 3


Tales from the Past

This section gives a few excerptsfrom past RAS Monthly Notices,BAA Journals and Sky &Telescope.

150 Years Ago: The editor notedthat, given the discoverycircumstances, he would prefer tocall Schweizer's comet (1849 G1)that of Schweizer-Bond, howeverhe followed the authority ofProfessor Schumacher.Computations by Hind showedthat the 'first Comet of Brorsen,1846' (5D/Brorsen) had passedvery close to Jupiter in May 1842.He further suggested that theremight be a link with the comets of1532 & 1661, which could beinvestigated further.

100 Years Ago: A paper read atthe June meeting discussed 'WhoFirst suggested the PeriodicalReturn of Comets' and suggestedthat Hooke had the idea thatcomets could return as early as1665, following the appearance ofthe comet of 1664, which Hookethought could be a return of thecomet of 1618 [it wasn't]. At thistime Halley was only 9 and didn'tvoice his famous utterance untilshortly before his death in 1742.At the same meeting a paper byMr John Grigg described agraphic method of computing asearch ephemeris for a periodiccomet. The annual report of theSection in the October Journal

records that two conspicuouscomets had been underobservation and that Tempel'scomet (10P) had been observed byMr Denning with a 10" (25 cm)telescope.

50 Years Ago: The July Journalhas a note about an article oncomet Families by C H Schwettewhich appeared in PopularAstronomy in April. He thoughtthat a group of comets withaphelia one and a half times thatof Pluto implied a tenth planet.The annual report notesobservations by George Alcockand Albert Jones, both still activeobservers.

Professional Tales

Many of the scientific magazineshave articles about comets in themand this regular feature is intendedto help you find the ones you'vemissed. If you find others let meknow and I'll put them in the nextissue so that everyone can lookthem up.

Andreas Kammerer has pointedout an interesting article by IchiroHasegawa and Syuichi Nakano onPeriodic Comets Found inHistorical Records in thePublications of the AstronomicalSociety of Japan (47, pp 699-710,1995). The authors have studiedobservations of comets reported inoriental manuscripts and havemade three linkages. Theysuggest that comet 1110 K1 was areturn of comet Pons-Gambart(see also The Comet's Tale No 8).Their linkage implies that itreturned unseen in 1956 and willreturn again in 2022. They alsolink 1500 H1 with 1861 J1, whichwould give a return in 2265 orthereabouts. The final linkage isfor 1337 M1 and 1468 S1, with aperiod of just over 130 years, andif this is correct the comet wouldhave returned in 1984. The cometis always well placed, so thefailure to see it suggests an errorin the period and that perhaps thecomet has not yet returned. Itmight be worth searching along atrack given by the approximateelements, which are given in theobserving supplement.

Jonathan Shanklin

The following abstracts (someshortened further for publication)

are taken from the CambridgeConference Network (CCNet),which is a scholarly electronicnetwork devoted to catastrophism,but which includes muchinformation on comets. Tosubscribe, contact the moderatorBenny J Peiser at<[email protected]>.Information circulated on thisnetwork is for scholarly andeducational use only. Theabstracts, taken from dailybulletins, may not be copied orreproduced for any other purposeswithout prior permission of thecopyright holders. The electronicarchive of the CCNet can be foundat http://abob.libs.uga.edu/bobk/cccmenu.html

A. Lewis Licht: The rate ofnaked-eye comets from 101 BCto 1970 AD. Icarus, 137 (2), pp355-356 February 99

The number of comets that arebright enough and that come closeenough to Earth to be seen withthe unaided eye fluctuatesrandomly from century to century.The mean number seen percentury, R, is a parameterdetermined by the distribution ofshort-period comets and by theescape of new, near paraboliccomets into the inner Solar Systemfrom the Oort Cloud (J. H. Oort,1963, The Solar System, Univ, ofChicago Press, Chicago, London)and the Kuiper Belt (H. F. Levisonand M. J. Duncan, 1997, Icarus127, 13-32). A measurement of Rprovides a constraint on possibleescape mechanisms. In thefollowing it is shown that R can be

determined by a comparison of thenumber of comets reported fromthe east and west with thosereported from both regions. Ananalysis of the reports compiledby I. Hasegawa (1980, Vistas inAstronomy, Pergamon, GreatBritain) shows that R = 86.0 +/-6.7 comets/century and moreoverR has been remarkably constantover the past two millennia. Onecould conclude from this that themean rate at which all comets,visible and invisible, enter theinner Solar System has also beenconstant over this period. © 1999Academic Press

E. Desvoivres, J. Klinger, A.C.LevasseurRegourd, J. Lecacheux,L. Jorda, A. Enzian, F. Colas, E.Frappa, P. Laques: Comet C/1996B2 Hyakutake: observations,interpretation and modelling ofthe dynamics of fragments ofcometary nuclei. MONTHLYNOTICES OF THE ROYALASTRONOMICAL SOCIETY,1999, Vol.303, No.4, pp.826-834

Comet C/1996 B2 Hyakutake wasextensively observed at the Pic duMidi observatory during lateMarch of 1996, Brightcondensations were observed inthe near-nucleus coma. We haveperformed a detailed data analysisin order to derive the position ofthese features with respect to thenucleus. We make the hypothesisthat they are induced by fragmentsof the nucleus. Despite thefrequency of fragmentation ofcometary nuclei, the dynamics ofthe fragments is not yet wellunderstood. We propose a general



approach in order to study themotion of the fragments in theorbital plane of the comet. Anestimate of the non-gravitationalforces is used to describe themotion of the fragment and of thenucleus with respect to their centreof mass. Then the equations of thetheory of perturbed Keplerianmotion are solved in order tostudy the motion of the centre ofmass, This approach is applied toComet C/1996 B2 Hyakutake, Theresults are in good agreement withthe observations, An excellent fitis obtained for a fragment size of20 m, assuming a density of 300kg m(-3). © 1999, Institute forScientific Information Inc.

S.H. Pravdo, D.L. Rabinowitz,E.F. Helin, K.J. Lawrence, R.J.Bambery, C.C. Clark, S.L. Groom,S. Levin, J. Lorre, S.B. Shaklan,P. Kervin, J.A. Africano, P.Sydney, V. Soohoo: The Near-Earth Asteroid Tracking(NEAT) Program: Anautomated system for telescopecontrol, wide-field imaging, andobject detection.ASTRONOMICAL JOURNAL,1999, Vol.117, No.3, pp.1616-1633

The Near-Earth Asteroid Tracking(NEAT) system operatesautonomously at the Maul SpaceSurveillance Site on the summit ofthe extinct Haleakala VolcanoCrater, Hawaii. The programbegan in 1995 December andcontinues with an observing runevery month. Its astrometricobservations result in discoveriesof near-Earth objects (NEOs),both asteroids (NEAs) and comets,and other unusual minor planets.Each six-night run NEAT coversabout 10% of the accessible sky,detects thousands of asteroids, anddetects two to five NEAs. NEAThas also contributed more than1500 preliminary designations ofminor planets and 26,000detections of main-belt asteroids.This paper presents a descriptionof the NEAT system and discussesits capabilities, including skycoverage, limiting magnitude, anddetection efficiency. NEAT is aneffective discoverer of NEAslarger than 1 km and is a majorcontributor to NASA's goal ofidentifying all NEAs of this size.An expansion of NEAT into anetwork of three similar systemswould be capable of discovering90% of the 1 km and larger NEAswithin the next 10-40 yr, while

serving the additional role ofsatellite detection and tracking forthe US Air Force. Daily updatesof NEAT results duringoperational periods can be foundat JPL's Web site(http://huey.jpl.nasa.gov/ similarto spravdo/neat.html). The imagesand information about the detectedobjects, including times ofobservation, positions, andmagnitudes are made available viaNASA's SkyMorph program. ©1999, Institute for ScientificInformation Inc.

NASA SELECTS MISSIONSTO A COMET'S INTERIORAS NEXT DISCOVERYFLIGHT

The Deep Impact mission willsend a 1,100-pound (500-kilogram) copper projectile intocomet P/Tempel 1, creating acrater as big as a football field andas deep as a seven-story building.A camera and infraredspectrometer on the spacecraft,along with ground-basedobservatories, will study theresulting icy debris and pristineinterior material. Dr. MichaelA'Hearn will lead Deep Impactfrom the University of Marylandin College Park.

Deep Impact will be launched inJanuary 2004 toward an explosiveJuly 4, 2005, encounter withP/Tempel 1. It will use a copperprojectile because that materialcan be identified easily within thespectral observations of thematerial blasted off the comet bythe impact, which will occur at anapproximate speed of 22,300 mph(10 kilometers per second.). Thetotal cost of Deep Impact toNASA is $240 million. DeepImpact will be managed byNASA's Jet Propulsion Laboratoryin Pasadena, CA, and built by BallAerospace in Boulder, CO.

Other comet missions include theStardust mission to gather samplesof comet dust and return them toEarth, which was launched inFebruary 1999. The Genesismission to gather samples of thesolar wind and return them toEarth and the Comet Nucleus Tour(CONTOUR) mission to flyclosely by three comets are beingprepared for launch in January2001 and June 2002, respectively.

Y.R. Fernandez, D.D. Wellnitz,M.W. Buie, E.W. Dunham, R.L.Millis, R.A. Nye, J.A. Stansberry,L.H. Wasserman, M.F. AHearn,C.M. Lisse, M.E. Golden, M.J.Person, R.R. Howell, R.L.Marcialis, J.N. Spitale: The innercoma and nucleus of CometHale-Bopp: Results from astellar occultation. ICARUS,1999, Vol.140, No.1, pp.205-220

We discuss the properties of thenucleus and inner coma of CometHale-Bopp (C/1995 O1) asderived from observations of itsoccultation of Star PPM 200723on 5 October 1996, while thecomet was 2.83 AU from the Sun.Compared to previous occultationsby active comets, this is possiblythe closest to the nucleus one hasever observed. Three chords(lightcurves) through the comet'sinner coma were measured, thoughonly one chord has a strongindication of measuring theoccultation, and that was throughthin cirrus. We have constrainedthe radius of the nucleus andproperties of the coma using asimple model; there is a largevalid section of parameter space.Our data show the optical depth ofthe coma was greater than or equalto 1 within 20 to 70 km of thecenter of the (assumed spherical)nucleus, depending on the coma'sstructure and the nucleus' size.The dependence of the dust coma'sopacity on cometocentric distance,rho, was steeper than expected forforce-free, radial how beingprobably as steep as or steeperthan 1/rho(1.4) within 100 km ofthe nucleus (though it ismarginally possible to fit onecoma hemisphere with a 1/rholaw), Assuming the dust comaflowed radially from a spot at thecenter of the nucleus and that thecoma's profile was not any steeperthan rho(-2) the upper limit to theradius of the nucleus is about 30km, though relaxing theseassumptions limits the radius to 48km, The chord through the comadoes not show the same comastructure within 100 km of thenucleus as that which is apparentin larger-scale (similar to 700km/pixel) imaging taken justbefore the event, suggesting that(a) the star's path sampled theacceleration region of the dust,and/or (b) azimuthal variation inthe inner coma is different thanthat seen in the outer coma. ©1999 Academic Press

1999 October 5


Review of comet observations for 1999 April - 1999 September

The information in this report is asynopsis of material gleaned fromIAU circulars 7139 – 7280 andThe Astronomer (1999 April –1999 September). Note that thefigures quoted here are roundedoff from their original publishedaccuracy. Lightcurves for thebrighter comets are fromobservations submitted to TheAstronomer and the Director. Afull report of the comets seenduring the year will be publishedin the Journal in due course.

Comet 10P/Tempel 2, made its20th observed return since itsdiscovery by William Tempel(Milan, Italy) as a 9m object in1873.

David Strange obtained an imageof the comet on July 10. Itbrightened rapidly. Jose Carvajalestimated it at 10.6 in his 32-cm Lon August 5.9, but I was unable tosee it with the 20-cmThorrowgood refractor on thesame night. On Aug 10.9 AndrewPearce and I observed it with14x100B from just outsidePenzance, Cornwall, my estimatewas 8.7 and Andrew made it alittle fainter. In Cambridge it wasa very difficult object in the 20-cmrefractor, though it was observedduring the IWCA. Back inAustralia Andrew Pearce reportedthat the comet had faded to near10m at the end of August.

77 observations give anuncorrected preliminary lightcurve of 5.8 + 5 log d + 32.2 log r

Comet 10P/Tempel 2

1999

Feb Mar Apr May Jun Jul Aug Sep Oct Nov

Obs

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18

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20

A few further observations ofComet 21P/Giacobini-Zinnerwere received after the last issueappeared, though they don'tchange the overall shape of thelight curve very much.


Comet 29P/Schwassmann-Wachmann 1. Reports suggestanother outburst to around 13m inearly June. Jose Aguiar reportedit in outburst once again at thebeginning of July.

Comet 37P/Forbes

1999

Mar Apr May Jun Jul Aug Sep Oct

Obs

erve

d m

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12

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16

Comet 37P/Forbes is currently14m, but is fading rapidly. 49observations give an uncorrectedpreliminary light curve of 10.6 + 5log d + 11.8 log r

A few further observations ofComet 52P/Harrington-Abellwere received, which give anuncorrected preliminary lightcurve following the secondoutburst of m = 10.2 + 5 log d +0.0416abs(t-T+23.1).

Comet/Asteroid 95P/Chiron wasaround 16m when at opposition inlate May in Libra. Maurice Gavinobtained images of the comet onJuly 10 and 11.

Comet 114P/Wiseman-Skiff willbe brightening from 14m inNovember and may be observedwith large aperture telescopes orCCDs.

Comet Hale-Bopp (1995 O1)

1995 - 1999

The residuals on the fitted curve are shown above.

SepDecMarJunSepDecMarJunSepDecMarJunSepDecMarJunSep

Obs

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aily

mea

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-4

-3

-2

-1

0

1

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12

Comet 1995 O1 Hale-Bopp , thegreat comet of 1997, is fadingslowly but is only observable fromSouthern Hemisphere locations asit loops round the LargeMagellanic Cloud. Anobservation by Andrew Pearce inlate August 1999 made it 12.5.

Over the entire apparition (750days with observations, spreadover 1532 days) the comet has thecorrected lightcurve of: -0.66 + 5log d + 7.59 log r There aresignificant variations from this,and the comet is currently a littlebrighter than indicated by thisequation.

Comet Spacewatch (1997 BA6)

1998 - 1999

Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

Obs

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12

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15

1997 BA6 Spacewatch Details ofthe orbit of an unusual asteroid,1997 BA6 were given on MPEC1997 C-13. The orbit is veryeccentric, with a period near 4500years and a semi-major axis ofseveral hundred AU. Currently itis near 13m and will be at highsouthern dec when near perihelionwhich is at 3.4 AU in 1999December when it may be around12m. 40 observations give anuncorrected preliminary lightcurve of 5.5 + 5 log d + 8.2 log r

Comet LINEAR (1998 M5)

1998 - 1999

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun

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1998 M5 LINEAR was atperihelion in January and passedvery close to the pole in midMarch. Heading south it passed



through Camelopardalus andLynx, reaching Cancer in midyear. 397 observations give anuncorrected preliminary lightcurve of 6.1 + 5 log d + 10.0 log r

1998 P1 Williams was widelyobserved from the UK afterperihelion. 126 observations givean uncorrected preliminary lightcurve of 6.7 + 5 log d + 9.9 log r

Comet Williams (1998 P1)

1998 - 1999

Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun

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1998 T1 LINEAR. SeiichiYoshida recovered the comet inlate April after conjunction but itsmagnitude was fainter thanexpected in his CCD images. Itbrightened and reached 9m in lateJune, but is now fading. 35observations give an uncorrectedpreliminary light curve of 10.2 + 5log d + 4.5 log r

Comet LINEAR (1998 T1)

1998 - 1999

Sep Oct Nov Dec Jan FebMar Apr May Jun Jul Aug Sep

Obs

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1998 U3 P/Jager Observationswith the Northumberland in Marchput the comet at 12m - 13m.Observing on April 9/10 I couldbarely see the comet in theNorthumberland, estimating it13.6. 157 observations give anuncorrected preliminary lightcurve of 9.8 + 5 log d + 0.0151abs(t-T-46.0). This is a linear typeof light curve and the comet beganfading before perihelion.

Comet Jager (1998 U3)

1998 - 1999

Nov Dec Jan Feb Mar Apr May Jun

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Only a few further observations of1998 U5 LINEAR were received.The 130 observations give anuncorrected preliminary lightcurve of 8.4 + 5 log d + 14.7 log r

Comet LINEAR (1998 U5)

1998 - 1999

Nov Dec Jan Feb Mar Apr May Jun

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1999 G2 SOHO (IAUC 7142,1999 April 14), 1999 H2 SOHO(IAUC 7147, 1999 April 19),1999 H4 SOHO (IAUC 7157,1999 May 3), 1999 J1 SOHO(IAUC 7162, 1999 May 10), 1999K1 SOHO (IAUC 7173, 1999May 20), 1999 K9 SOHO (IAUC7204, 1999 June 18), 1999 K10SOHO (IAUC 7204, 1999 June18), 1999 L1 SOHO (IAUC7197, 1999 June 11), 1999 L4SOHO (IAUC 7204, 1999 June18), 1999 L5 SOHO (IAUC7208, 1999 June 25), 1999 M1SOHO (IAUC 7208, 1999 June25), 1999 M2 SOHO (IAUC7212, 1999 June 30), 1999 N1SOHO (IAUC 7213, 1999 July 1),1999 N3 SOHO (IAUC 7222,1999 July 14), 1999 P2 SOHO(IAUC 7234, 1999 August 9),1999 S1 SOHO (IAUC 7256,1999 September 17) weresungrazing comets discoveredwith the SOHO LASCOcoronographs and have not beenobserved elsewhere. Severalothers have yet to receivedesignations. SOHO has nowdiscovered 89 comets, of which 84are members of the Kreutz groupof sungrazing comets.

1999 K1 was one of the brighterobjects. On May 20.47 UT, thecomet was about 11 solar radiifrom the sun and showed a tail; onMay 20.51 it was 6.8m. Astandard magnitude predictionsuggested it could reach -4magnitude, however as with mostof the Kreutz group fragments itfaded as it got closer to the sun.Some of the comets show no tail atall and it is possible that somesupposed observations of Vulcanwere actually tiny Kreutz groupcomets.

I discovered SOHO-86=1999 S1on the morning of September 17and the discovery has a storybehind it.

A discovery frame of comet 1999 S1. Thecomet is shown circled.

The University of CambridgeCavendish Laboratory hosts a'Physics at Work' Exhibition inmid September, which is designedto get prospective GCSE studentsenthusiastic about following acareer in physics. I usually run anexhibit about work at the BritishAntarctic Survey (BAS), whichshows the students the physicsbehind measuring ozone in theatmosphere. This year we wereasked to put on two exhibits andfor a variety of reasons I ended upteaching the students about'geospace'. I had been looking atthe real-time movies of theLASCO C3 camera for severalmonths on an occasional basis andwas impressed by how well theyshow the dynamic activity of theSun. I thought it would beeducational to show the studentslive images of the Sun, so Idownloaded the images everymorning and showed the currentmovie loop. There were nocomets during the exhibition, butthe planet Mercury was visibleheading out from superiorconjunction. I also showed anarchival image, which did show acomet, to illustrate that comet tails

1999 October 7


always point away from the sun,thus demonstrating the existenceof the solar wind.

Having packed everything up onFriday morning (September 17th),I cycled back to BAS and decidedto have a look at the latestsequence from the wide field C3camera. A quick scrutiny showeda star-like object heading towardsthe Sun and brightening, butwithout a tail. The object becamevisible at about 15:18 UT onSeptember 16 and was brighteston the most recent frame to bedownloaded, which was taken at05:18. I guessed that it was aprobable Kreutz group fragment,though expected someone else tohave picked it up already. At09:41 UT, I e-mailed DougBiesecker of the SOHO-LASCOconsortium to inform him of theobject, with a copy to Dan Greenat the CBAT. Doug responded at12:32, and confirmed that it was aprobable Kreutz group fragmentand that I was the first to report it.He measured the images andquickly passed the details on tothe CBAT. Brian Marsden wasable to compute a preliminaryorbit whilst the object was stillvisible in the coronagraphs. Thepositions and orbit appeared onMPEC 1999-S04, issued at 15:26and a note recording the discoveryappeared on IAUC 7256 at 17:08.The orbit shows that it is anothermember of group I of the Kreutzfamily of sungrazing comets. Thefragment grew a short tail, visibleon the C2 frames, but then fadedas it dived towards the sun. Thelast available image to show it thatday was taken at 16:54, thougharchival images record it a littlelonger.

The comet is the radial streak in thebottom right corner.

1999 DN3 P/Korlevic-Juric The19m, apparently asteroidal object1999 DN3, observed by K.Korlevic and M. Juric at Visnjan

(0.41-m f/4.3 reflector + CCD) onFebruary 18.97 and 24.0 UT(MPC 33833, MPS 4018), waslinked by G. V. Williams, MinorPlanet Center, to observations onApril 6 and 14 in routineasteroidal astrometry fromLINEAR. Owing to the unusualnature of the orbit, computed onMay 13, the object was added toThe NEO Confirmation Page. Inresponse to this, furtherobservations were reported onMay 14.2 by D. A. Klinglesmith,III, and R. Huber (EtscornObservatory) and by G. Hug(Farpoint Observatory). Williamsalso identified LONEOSobservations of the object on Apr.10. In addition, C. W.Hergenrother, Lunar and PlanetaryLaboratory, reported thatobservations made on May 14with the 1.5-m Catalina reflectorshowed the object to be cometary,with a compact, well-condensed10" coma and a strongly curved30" tail, starting in p.a. 45 deg andcurving to p.a. 335 deg. [IAUC7167, 1999 May 14]. The cometis distant and fading.

1999 F1 CATALINA On Apr.17, T. B. Spahr, Lunar andPlanetary Laboratory, reported theautomatic discovery of an 18m

object of unusual motion andstellar appearance in the course ofthe Catalina Sky Survey (0.41-mSchmidt + CCD) on March 23.32.Spahr obtained follow-up data onApr. 16 and 17. Computations byB. G. Marsden suggested that theobject was a long-period comet ina highly-inclined orbit, yielding anidentification in Mar. 13Spacewatch data. CCD images(660 s total exposure) obtainedwith the Catalina 1.5-m reflectorby J. Bialozynski, D. Dietrich, C.Greenberg, E. Hooper, D. McBee,D. McCarthy, J. Pici, G. Rudnick,and C. Vedeler, and co-added byC. W. Hergenrother, show a faintcoma of diameter 8"-10" [IAUC7148, 1999 April 20]. The cometis currently very distant (over 8AU) and not due to reachperihelion until 2002, but eventhen it will be 5.8 AU from theSun.

1999 F2 Dalcanton JulianneDalcanton, University ofWashington; S. Kent, FermiNational Accelerator Laboratory;and S. Okamura, University ofTokyo, on behalf of the SloanDigital Sky Survey (SDSS),reported the discovery byDalcanton of a comet on severalSDSS images taken on March 20

through different filters. An r'-band filter shows a tail about 2'long and a sharp nucleus inside acoma of diameter about 20".Upon receipt at the CentralBureau on June 7 of theastrometry, spanning only 72 s oftime, G. V. Williams found apossible link with a single-nightapparently asteroidal LINEARobject in archival data for March24; this permitted Williams to findfurther apparently asteroidalLINEAR observations, first onFeb. 23, then on May 12, andfinally on 1998 June 18. At thispoint, the object was placed on theNEO Confirmation Page inexpectation that additionalobservations would confirm thecometary nature. In response,confirming CCD observationsshowing cometary appearancewere received from M. Tichy andZ. Moravec at Klet on June 7.9UT (coma diameter 15", tail 50"in p.a. 230 deg) and from R. A.Koff at Thornton, CO, on June 8.2(15" coma, 35" tail in p.a. 195deg). Dalcanton subsequentlyforwarded single-night LONEOSobservations obtained on March28 and found by G. Magnier.[IAUC 7194, 1999 June 8]. Thecomet is distant, but intrinsicallyquite bright. It will fade from itscurrent 15m.

1999 G1 LINEAR another objectdiscovered by LINEAR has beenidentified as a comet [IAUC 7140,1999 April 10]. The 17m object isin a distant parabolic orbit andwill fade.

1999 H1 Lee Steven Lee (a nightassistant at the Anglo-AustralianTelescope in New South Wales)discovered this 9m comet on April16.5 with a 0.41-m f/6 Newtonianreflector (about x75) at a star partynear Mudgee, New South Wales[IAUC 7144, 1999 April 16].

Comet Lee (1999 H1)

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difficult object in a bright twilightsky. It has faded and becomemore diffuse. Several observersimaged an anti-tail in September.


1999 H3 LINEAR An apparentlyasteroidal 17th mag objectdiscovered by LINEAR on April22.31, and noted on The NEOConfirmation Page, was reportedas cometary by Klet and Ondrejovobservers [IAUC 7151, 1999April 23]. The comet is in adistant parabolic orbit and didn'tbecome much brighter than 13m.

38 observations give a somewhatindeterminate uncorrectedpreliminary light curve of 8.7 + 5log d + [5] log r

Comet LINEAR (1999 H3)

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1999 J2 Skiff Brian Skiff of theLowell Observatory Near-EarthObject Search (LONEOS) teamdiscovered a 16m comet on May13.40 [IAUC 7165, 1999 May13]. The comet is at high northerndeclination, and is very distant atover 7 AU, with perihelion inOctober 1999. It will remain near15m for some time.

1999 J3 LINEAR An apparentlyasteroidal 19m object discoveredby LINEAR on May 12.28, andnoted on The NEO ConfirmationPage, was reported as cometary byKlet observers [IAUC 7166, 1999May 13]. Estimates in mid Julyput it at 12m. By early Septemberit had reached 10m. It was 9.6 in20x80B from a dark sky site onSeptember 12.1, rather smallerthan comet Lee. It peaked inbrightness at around 7m in midOctober. It is currently small andwell condensed.


Comet LINEAR (1999 J3)

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1999 J4 LINEAR Anotherasteroidal object reported byLINEAR on May 15.32 UT (mag18.2-18.8) with unusual motionwas noted on The NEOConfirmation Page, and it wassubsequently reported to becometary in appearance by severalobservers, including M. Elowitzand F. Shelly from May 17LINEAR observations. P. Pravec,U. Babiakova, and P. Kusnirak(Ondrejov, 0.65-m f/3.6 reflector+ V filter) reported a comadiameter of 0'.2 and a tail 0'.6 longin p.a. 160 deg, and J. Ticha andM. Tichy (Klet, 0.57-m f/5.2reflector) noted the object to beslightly diffuse (coma diameterabout 7"), on May 16.9 [IAUC7170, 1999 May 17]. The cometis in a distant parabolic orbit.

1999 J5 P/LINEAR Anapparently asteroidal 19m objectreported by LINEAR on May12.36 and 17, and linked by G. V.Williams to LINEAR observationson June 8 and 10 by way of acomet-like orbit, was posted onThe NEO Confirmation Page foradditional observations. P. Pravecand P. Kusnirak, Ondrejov,reported that their June 12 CCDimages showed a faint coma and atail marginally visible to thesouthwest. Also, A. Sugie, DynicAstronomical Observatory,reported strong condensation anda coma diameter of 12" on June 14[IAUC 7201, 1999 June 14]. Thecomet will fade.

1999 K2 Ferris William D. Ferrisdiscovered an 18th mag comet onCCD frames taken with the 0.59-mLONEOS Schmidt telescope onMay 19.37. Measurer B. Koehnnoted that the comet showed awell-condensed nucleus, a coma ofdiameter about 15", and a faint tailabout 20" long in p.a. 225 deg onMay 19. Additional astrometryappeared on MPEC 1999-K22.May 22 observations by J. Tichaand M. Tichy (Klet) showed the

comet as diffuse with a 12" coma;observations on the same night byL. Kornos and P. Koleny (Modra)also showed a coma. C. W.Hergenrother and A. E. Gleason(Catalina 1.5-m reflector) reporteda 20" coma and a 20" tail in p.a.230 deg. [IAUC 7175, 1999 May22]. The comet is in a distantparabolic orbit and won't brightenmuch from its present visualmagnitude of around 16.

1999 K3 LINEAR M. Elowitz,Lincoln Laboratory,Massachusetts Institute ofTechnology, reported thediscovery of 19m, apparentlycometary object in LINEAR dataon May 20.27. Following postingof this object on The NEOConfirmation Page, numerousobservers confirmed the cometaryappearance, and additionalastrometry and orbit were givenon MPEC 1999-K23. Around May22.0 UT, L. Sarounova (Ondrejov)reported coma diameters about20" and 15"; Ticha and Tichyreport a 10" coma and a wide tailin p.a. 245 deg; and coma was alsonoted by Kornos and Koleny.[IAUC 7175, 1999 May 22]. Thecomet is past perihelion and isfading from visual magnitude 16.

1999 K4 LINEAR Anotherapparently asteroidal object of 19m

found by LINEAR on May 17.33,and posted on The NEOConfirmation Page, was reportedas cometary by M. Hicks (TableMountain; faint coma of diameterabout 5" on May 21) and by C. W.Hergenrother and A. E. Gleason(Catalina 1.5-m reflector; highlycondensed coma with a faint 10"-15" tail in p.a. 170 deg on May22) [IAUC 7176, 1999 May 22].The comet is intrinsically faint andwill fade.

1999 K5 LINEAR Anotherapparently asteroidal, 17m objectdiscovered by LINEAR on May20.32 and posted on The NEOConfirmation Page, was reportedas cometary by several observers.CCD frames taken by D. D. Balam(Victoria) on May 23 show acondensed coma with a 16" fan-shaped tail in p.a. 303 deg. OnMay 24, L. Kornos and P. Koleny(Modra) report a coma diameter ofabout 15" and a short tail in p.a.330 deg, and G. Hug (FarpointObservatory) indicated a hint ofcoma in p.a. about 300 deg.[IAUC 7178, 1999 May 24]. Thisis LINEARs 23rd discovery inaround 14 months. The comet iscurrently around 16m visually, and

1999 October 9


does not reach perihelion until2000 July, by which time it mayhave brightened to around 13m. Itwill however be at high southerndeclination.

1999 K6 LINEAR Yet anotherapparently asteroidal object, of18m, discovered by LINEAR onMay 20.23, and posted on TheNEO Confirmation Page, wasreported as cometary, on May 24by L. Sarounova (Ondrejov; faintcoma with condensed nucleus) andby M. Tichy and Z. Moravec(Klet; diffuse with coma diameter/= 10") [IAUC 7180, 1999 May25]. The comet will brighten alittle, but is unlikely to do betterthan 15m.

1999 K7 LINEAR A 19m objectdiscovered by LINEAR on May24.34 was reported as possiblycometary by M. Elowitz, LincolnLaboratory, with an apparent tailin p.a. about 220 deg.Confirmation of cometary activitywas made by D. D. Balam(Victoria), who noted no tail butmeasured a 7" diffuse coma.[IAUC 7181, 1999 May 26] Thecomet will fade from its presentmagnitude.

1999 K8 LINEAR Anotherapparently asteroidal 19m objectdiscovered by LINEAR on May26.38 and posted on The NEOConfirmation Page, was reportedas cometary on May 27 by L.Sarounova (Ondrejov; comadiameter at least 30" withcondensed nucleus), by M. Tichyand Z. Moravec (Klet; 10" coma),and by R. A. Koff (Thornton, CO;diffuse coma of diameter about8") [IAUC 7182, 1999 May 27].The comet is a distant one and willremain near 14m until 2000.

12 observations give anuncorrected preliminary lightcurve of 1.8 + 5 log d + [15] log r

1999 L2 LINEAR M. Elowitzand F. Shelly reported thediscovery of a 18m comet with acoma but no distinct tail inLINEAR data on June 11.24. Inresponse to posting on The NEOConfirmation Page, G. R.Viscome (Lake Placid, NY)reported that the object showed a16" coma and moderately strongcondensation, but again nodiscernible tail [IAUC 7199, 1999June 12]. The comet is around16m visually and reachedperihelion in August.

1999 L3 LINEAR An 18th magapparently asteroidal fast-movingLINEAR object found on June9.17 and posted on The NEOConfirmation Page, was noted byF. B. Zoltowski, Woomera, S.Australia, as having a tail about30" long in p.a. 100 deg and arather dense coma on June 13 and14 CCD images. P. R. Holvorcem,Valinhos, Brazil, reports a about10" coma on his June 12 images.[IAUC 7200, 1999 June 14]

A/1999 LD31 and A/1999 LE31MPEC 1999-M28 and 1999-M29provided detailed informationabout two apparently asteroidalobjects, 1999 LD31 and LE31,discovered by LINEAR on June 8and 12, respectively (withprediscovery observations of thelatter on May 17), and followedextensively by observers usingThe NEO Confirmation Page. Ineach case the orbit was found tobe retrograde: 1999 LD31 has a =21.9 AU, e = 0.89, i = 160 deg,P=103 years, H = 13.9; 1999LE31 has a = 8.0 AU, e = 0.46, i =152 deg, P=23 years, H = 12.3.All observers consistently reported1999 LD31 to be asteroidal, andonly one observer suggested that1999 LE31 may have cometaryappearance (although this isunconfirmed). In particular, A.Fitzsimmons, Queen's University,Belfast, reported that 250-sexposures in 1" seeing by S.Collander-Brown and S. Lowrywith the 1-m Kapteyn telescope atLa Palma on June 15 show bothobjects clearly to be point sources.[IAUC 7208, 1999 June 25]

1999 N2 Lynn Daniel W. Lynn,Kinglake West, Victoria,Australia, visually discovered an8m comet using handheld 10x50binoculars on July 13.45 [IAUC7222, 1999 July 14]. I glimpsed itin 20x80B on August 5.9 at 7.7,and Jose Carvahal also estimatedit at 7.7. I made a furtherobservation in company withAndrew Pearce on August 10.9and estimated the comet at about7.6 in 20x80B. The comet willcontinue to fade slowly and willbecome a morning object.


Comet Lynn (1999 N2)

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1999 N4 LINEAR (L-30) Yetanother LINEAR discovery withunusual motion, which was placedin The NEO Confirmation Pageand found to have a retrogradeorbit. At the request of theCentral Bureau, some of theobservers making astrometricobservations examined theirimages carefully and concludedthat the object was a comet. M.Tichy (Klet, 0.6-m reflector) notedcomae of diameter about 6" onJuly 14.9 and about 7" on July15.9 UT. L. Sarounova(Ondrejov, 0.6-m reflector)indicated a small coma, some lackof condensation but no tail on July16.9. F. B. Zoltowski (Woomera,0.3-m reflector) remarked on acompact, diffuse image with anasymmetrical distribution that mayindicate a small, faint tail at p.a.around 90 deg on July 17.6 [IAUC7226, 1999 July 17]. The comethas m2 around 18m and is a distantobject, reaching perihelion nextyear.

Robert H. McNaught recoveredComet 1999 P1 141P/Machholz2 on CCD images obtained withthe 1.0-m f/8 reflector at SidingSpring on August 3.55. Theobject was of stellar appearance.The indicated correction to theprediction by B. G. Marsden onMPC 27082 (for component A) isDelta T = +0.8 day. Seeing wasgood on Aug. 4, and there was nosign of any other componentswithin Delta T = +/- 1.5 days.Further orbital computations byBrian Marsden confirmed that ifthe observations were of the sameobject that was observed at SidingSpring on 1995 Mar. 29 and 30(MPC 25097), this is indeedcomponent A. However, attemptsto link all the observations (backto 1994 Aug. 15), even using thenongravitational parameters A1and A2, were not satisfactory. Agravitational solution gives anacceptable fit to 67 observationsback to 1994 Oct. 2 (mean



residual 0".9; earlier residualsincreasing to 20") [IAUC 7231,1999 August 04] Z. Sekanina(1999, A & Ap 342, 285; Table 7)tabulates the expected offsets ofcomponents B and D fromcomponent A. In terms of Delta T,these amount to +0.21 and +0.82day, respectively. [IAUC 7232,1999 August 04] The expectedmagnitude this autumn is still alittle uncertain.

1999 R1 SOHO =SOHO 85 DougA. Biesecker, SM&A Corporationand Goddard Space Flight Center,reported observations of what waspresumably a comet, not a Kreutzsungrazer, discovered by T.Lovejoy in SOHO/LASCO C3data and later also recognized inearlier C2 data. It was observedfrom September 4.90 toSeptember 6.26, reaching 6th magat best and no tail was detected.[IAUC 7251, 1999 September 9]

1999 R2 142P/Ge-Wang JimScotti, Lunar and PlanetaryLaboratory, recovered cometP/1988 V1 (= 1988o = 1988 VIII)with the Spacewatch 0.9-mtelescope at Kitt Peak onSeptember 15.44. The nuclearmagnitude m2 was 22.1. OnSeptember 15 there was a coma12" across and a tail extending0'.53 in p.a. 266 deg. OnSeptember 16 the coma diameterwas 11", and the tail extended0'.47 in p.a. 267 deg. Theindicated correction to theprediction by S. Nakano on MPC27081 was Delta T = -5.5 days.The comet is unlikely to becomebrighter than 19th mag. [IAUC7255, 1999 September 17].

1999 RO28 P/LONEOS C.Hergenrother, Lunar and PlanetaryLaboratory, reported that a co-added 600-s CCD exposure withthe Steward Observatory 2.3-mreflector on Sept. 13 of 1999

RO_28 (discovered by LONEOSon September 7.33, with detailsgiven on MPEC 1999-R23)showed a stellar condensation witha faint 20" tail in p.a. 310 deg. M.Tichy and J. Ticha, Klet, laterreported a faint coma of diameter8" and 7" on images taken onSept. 8.93 and 10.02 UT,respectively. Observations by J. V.Scotti with the Spacewatchtelescope at Kitt Peak on Sept.15.4 showed a coma diameter of9" (m_1 = 18.6-18.7, m_2 = 20.6-21.0) and a 0'.72 tail in p.a. 308deg. [IAUC 7253, 1999September 15]. The comet has a6.5 year period and will fade as itrecedes from the Earth.

1999 S2 McNaught-Watson RobH. McNaught, Australian NationalUniversity, reported his discoveryof a comet on an R survey filmtaken with the U.K. SchmidtTelescope by F. G. Watson onSeptember 19.72. The cometshowed a very strong centralcondensation, a weak circularcoma of diameter 20", and adiffuse tail 3'.5 long in p.a. 210deg. Confirming CCD images byMcNaught with the 1.0-m f/8reflector at Siding Spring taken onSeptember 21.6 yielded m_2 =20.1-20.2 [IAUC 7260, 1999September 21]. The orbit showsthat the comet is intrinsicallybright, but very distant andperihelion was a couple of yearsago.

1999 S3 LINEAR (L-31) M.Bezpalko reported the discoveryby LINEAR of a 16m comet onSeptember 24.34. Followingposting on the NEO ConfirmationPage, additional observations werereported, giving m1 near 13m

[IAUC 7264, 1999 September 24].The comet has a period of around80 years and reaches perihelion inearly November. It will brighten alittle before fading. It was

surprisingly easy in theNorthumberland refractor onOctober 2.90, although the BAAVS sequence for RX And put it at13.6. Transparency was verygood and I could see star S of thesequence, which is magnitude15.6.

1999 S4 LINEAR (L-32) Anotherunusual-moving object of 17m

discovered by LINEAR onSeptember 27.40, reported asasteroidal and subsequently postedon the NEO Confirmation Page,was noted to be cometary inappearance by D. Durig (Sewanee,TN, 0.3-m f/7 reflector + CCD;coma diameter about 10"; tailabout 20"-25" long in p.a. 200-220 deg) and by J. Ticha and M.Tichy (Klet, 0.57-m f/5.2 reflector+ CCD; comet diffuse with 8"coma and tail 10" long in p.a. 245deg). The preliminary parabolicorbital elements suggest that thiscomet might become a naked-eyeobject next July [IAUC 7267,1999 October 1]. The comet willbrighten to within reach of visualobservers early next year beforesolar conjunction. Afterconjunction it will brighten rapidlyto become a naked eye object inthe northern sky. Full details willappear in the next issue.

Stop press. 1999 T1(McNaught-Hartley) may be abinocular object in December2000 and 1999 T2 (LINEAR)may reach 13m in late summer of2000. More details in the nextissue.

For the latest information ondiscoveries and the brightness ofcomets see the Section www page:http://www.ast.cam.ac.uk/~jdsor the CBAT headlines page athttp://cfa-www.harvard.edu/cfa/ps/Headlines.html

Comet Hunting Notes

Don Machholz

MAY 1999: Of the 79 cometsvisually discovered since 1975, 36were found in the southern sky.These southern discoveries werenot evenly spaced throughout theyear. Exactly half (18) of themtook place in about three months-between Nov. 23 and Feb. 25.(During that same time only eightNorthern Hemisphere findsoccurred.) Good summer weather

in the Southern Hemisphere doesnot account for all the finds; eightof those 18 discoveries were madeby Northern Hemisphere comethunters searching the southernskies. So when did NorthernHemisphere finds prevail?Between mid-March and mid-June, 11 of the 12 finds occurredin the northern sky.

JUNE 1999: Comet Lee is one offour comets found by amateurs atstar parties during the past 25years. In 1975 Doug Bergerfound Comet Kobayashi-Berger-Milon while looking for M 2 at aSan Jose AstronomicalAssociation event. In 1985 Ifound Comet Machholz (1985e) atthe Riverside Telescope Makers'Conference. In 1995, at a star

1999 October 11


party in Arizona, Thomas Boppfound a comet near M 70. Threeof these four finds were accidentalfinds, and those three cometsreached magnitude seven orbrighter.

JULY 1999: Steve Lee's cometdiscovery in April was the thirdaccidental find of the past sixSouthern Hemisphere visual cometdiscoveries. That is a highpercentage considering that thereare only two other accidental findsamong the 80 discoveries visuallyfound since 1975. What does thismean? Are comet hunters gettinglazy? If the comets were outsidetypical comet hunting areas, thencomet hunters would tend to missthem. For two of the comets thismay be true, as the discoveryelongations of all three were 72,103, and 120 degrees from thesun. And if the comets brightenrapidly before discovery, then theusual comet hunting methods maymiss them. A third reason for moreaccidental finds is an increase ofactivity among non-comet hunters.With the Internet making it easierto report suspicious objects, andthe Wilson award motivating thereporting of new comets, it islikely that accidental cometdiscoveries by amateurs willcontinue at a brisk rate in theSouthern Hemisphere, which isnot covered well by the automatedsearch programs.

AUGUST 1999: Fifty-two of the80 comets discovered by amateursover the past 24 years haveperihelion distances of less than1.0 Astronomical Unit (AU). At

the extremes we have a minimumdistance of 0.11 AU for a cometfound by me in 1985, and amaximum distance of 3.32 AU fora comet found by K. Cernis in1983. Now contrast that to theSOHO satellite whose discoverieshave perihelion distances of under.01 AU and to LINEAR, which isfinding many comets withperihelion distances of greaterthan 3.0 AU.

SEPTEMBER 1999: Lynn'sdiscovery is the fourth consecutivecomet to be visually discoveredfrom Australia, and all four havebeen found in the past 12 months.Of the last nine comets foundvisually, seven have beendiscovered by Australians.

OCTOBER 1999: CometLINEAR (1999 J3) discovered onMay 12, has left the polar regionand entered our morning sky,brightening rapidly. Imagine mysurprise when I recently swept itup while comet hunting, notknowing it would be so bright.The tilt of the comet's orbit iscalled the inclination, and it ismeasured in degrees. A cometgoing in earth's orbit has a 0degree inclination, while onegoing in the opposite direction hasa 180 degree inclination. Anobject travelling perpendicular toearth's orbit (as does Comet Hale-Bopp) has an inclination of 90degrees. The average inclinationfor the last 81 visually foundcomets is 84 degrees. There is aslight grouping of comets in the40-50 degree range and a dearth ofcomets near 100 degrees. I

suspect this is a true picture ofcomet orbit distribution, sincecomet hunter sweeping patternswould not seem to favour (andunfavour) these particularinclinations.

Don's Comet Hunting HoursComet Hunting Hours 1975-1998:6468.00Additional hours in 1999: 117.00Total hours at last discovery (10-8-94): 5589.00 (nearly 1,000hours ago)Least hours in any month since hebegan comet hunting on 1/1/75:4.00 (02/98), 4.50 (01/86), 5.50(02/80)Most hours in any month since hebegan comet hunting: 69.25(05/76), 63.00 (05/78)

These notes are taken from CometComments by Don Machholz,which is published on the Internet.

The Edgar Wilson award for 1999was announced on IAUC 7223 onJuly 14 and was divided amongthe following six individuals orgroups: Peter Williams,Heathcote, N.S.W., Australia, forC/1998 P1; Roy A. Tucker,Tucson, AZ, U.S.A., for P/1998QP54; Michael Jager,Weissenkirchen i.d. Wachau,Austria, for P/1998 U3; JustinTilbrook, Clare, S.A., Australia,for C/1999 A1; Korado Korlevicand Mario Juric, Visnjan, Croatia,for P/1999 DN3; and Steven Lee,Coonabarabran, N.S.W.,Australia, for C/1999 H1.

International Workshop on Cometary Astronomy

Continued from page 1The average elongation is 70 deg.Most are 20 to 60 altitude andaverage 9.4 mag. They areslightly brighter closer to the sun,but not much. Some bright comets(6th mag) have been found farfrom the Sun. Amateurs average3.3 per year, with an average of368 hours per comet and a medianof 177 [NH 433/228, SH165/113]. Average q is 0.9.

Kesao Takimizawa addressed themeeting on Japanese cometdiscoverers. He had becomeinterested in astronomy in 1966aged 14, and had observed Ikeya-Seki. He had searched for 33years and discovered 5 comets.The first Japanese cometdiscovery occurred in 1928.

Honda had been very successfulwith 12 comets, followed by Ikeyaand Seki. Several Japanesediscoveries were madesimultaneously by three or moreobservers. 57 visual Japanesediscoverers have found comets,with 72 in total (14 photographicand one CCD). Most usedreflectors or binoculars, and 113different instruments had beenused. He has used largebinoculars for 15 years. A plot ofdiscoveries showed that they weremostly morning, followed byevening and opposition, with gapsbetween opposition andquadrature, particularly in theevening sky. He showed prints ofJapanese discoverers andmentioned a medal for Japanesediscoverers.

Alan Hale and Kesao Takamizawa.

After a break for refreshmentscame a panel discussion onhunting for comets, however Imissed most of these whilstcarrying out administrative duties.LINEAR doesn’t search within 90deg of the sun, and there is nomove to set up a Southern



Hemisphere equivalent. TheEdgar Wilson award wasdiscussed, most panellists didn’tthink it would make muchdifference, but it was nice to havethe money. One negative aspect isthe feeling of financial loss whensomeone else discovers a comet.

Michael Jager had madeaccidental discoveries as a resultof photographing other comets.He had found a fragment ofMachholz 2 (what should this becalled if it turned out to be themain fragment?) and P/1998 U3whilst photographing Harrington-Abel. He uses Schmidt cameras,the smaller reaching 14m and thelarger 15m and has photographedover 150 comets. He thanked thediscoverers for providing him withopportunities for photographingnew comets. He beganphotographic work in 1982 andhad failed to see comet Kohoutek.

We broke for a buffet lunch,which turned out to be anotherfilling meal, with more than justbites on offer. After lunch CharlesMorris spoke to the title "Why youdon't get your papers published inthe ICQ and other rants". Hebegan by defining a rant as aheated one sided discussion. Histopic was on amateur research.Many amateurs observe at aprofessional level. The ICQwould like to publish amateurpapers, but their quality is oftenbelow the acceptable standard.

To demonstrate the problem thatoccurs with some amateurpublications, he cited a situation atthe last IWCA where informalexchange about his use of avertedvision was then used as the basisof a paper to (incorrectly)discredit the Morris magnitudeestimation method. This paperwas published in an amateurcomet publication and neither theauthor nor editor bothered tocheck the validity of the referenceto the informal conversation. TheICQ tries to avoid such problemsby using a referee review system.

As a side note, he pointed out thatthe Morris method actuallyintegrates the Sidgwick andBobrovnikoff methods. That is,when properly used these twomethods are actually subsets of theMorris method. Morris thenasserted (Charles Morris personalcommunication!) that using theSidgwick technique for DC3+ orBobrovnikoff method for DC7-will give biases brighter and

fainter, respectively. In discussionNick James pointed out that thisassertion about the Morris methodwas not proven; Charles was notallowed to forget it for the rest ofthe meeting, though hecommented that the underestimateof the Bobrovnikoff method waswell documented. Joe Marcuslater commented that the extensivework by the Dutch comet sectiondid demonstrate the delta effect.

Morris noted that several groupswant additional observationalinformation to be published in theICQ tabulations. However, priorto adding parameters, it must beshown that the information wouldbe useful. This is theresponsibility of the person/groupproposing the parameters, not theICQ staff. Adding additionalparameters to the database,particularly for past observations,is non-trivial. It will be done (forinstance, the changes made in theDC parameter after the lastIWCA) when the change clearlyimproves the database.

Most amateur research requiresstatistics. Statistics are veryimportant and you can't just asserta correlation. There is adifference between precision andaccuracy and you need to quoteerrors. The delta effect may exist,but as r and delta are correlated,any delta effect study must notblindly use multiple regressionanalyses. (Morris has yet to beconvinced that the delta effect hasbeen proven.) Extrapolation alsopresents problems whenobservations only cover a limitedmagnitude range. Adding extraparameters, eg coma diameter,doesn't necessarily improveestimates or analyses of M1,particularly if the parameter ispoorly defined. Morris' advicewas to listen to reviewerscomments, they should help toimprove the paper, thoughreasoned argument can convincean editor that the reviewer isincorrect.

The next item was a paneldiscussion between CharlesMorris, Jonathan Shanklin, GuyHurst, Dan Green and AndreasKammerer on the World WideWeb, the Internet and theinfluence on comet observing.Although there had been somefeeling that the new media acted tobias observers, there was littledemonstrable evidence. GuyHurst made the point that thescatter in variable star estimates

was typically no more than ±0.8whilst the scatter in cometobservations was often 2magnitudes. When the extremeobservations were queried theobservers sometimes admitted thatthey were guestimates rather thanactual observations. There mightbe a case for always including theactual magnitude estimate inreported observations, as is donewith variable stars. Magnitudeestimates of comet Hyakutakewere quite discordant, withexperienced and inexperiencedobservers making systematicallydifferent estimates. It was pointedout that the telephone had existedbefore the Internet and that it hadalways been possible to exchangeinformation. Charles Morris saidthat he regarded the Internet as aneducational tool, and the beginnerobservers would eventuallybecome experienced.

Andreas Kammerer commentedthat the long tails reported forcomet Hyakutake were physicallyimpossible. The waxing mooncoincided with the publication ofIAUC 6360, which first castdoubts on these estimates, thuspreventing further observations,which might have settled thequestion of influence onobservers. The tail had shrunksignificantly by the time the moonwaned after closest approach. Inhis poster Andreas showed resultsof his investigations on thismatter: the contentiousobservations can only beexplained by the somewhatdubious assumption of a tail thatmust have deviated in step withthe changing position of the earth.

After the discussion, tea was alittle delayed and we took theopportunity for the first groupphotograph. Following the breakHerman Mikuz explained hiscareful procedures for CCDphotometry [I missed this talkwhilst finding new supplies ofposter pins and mains adaptors.]Nicolas Biver spoke on his workon the outgassing of carbonmonoxide from distant comets.He concluded that there was agood correlation between visualmagnitude and CO outgassing. Hesuggested that any comet brighterthan 14th magnitude should beobservable if CO drives theactivity, even out to 30 AU.

A panel discussion betweenCharles Morris, Dan Green,Herman Mikuz, Nicolas Biver andfor the last few minutes Jonathan

1999 October 13


Shanklin followed. Oneconclusion was that a groupshould be set up to discuss theissues of CCD photometry and setup standard procedures. JonShanklin commented that currentICQ coding didn’t include a codefor the type of CCD chip beingused in the photometry.

As the weather looked a bitthreatening (we had heard thunderrolling around and a gust front hadthrown up dust outside thecollege), a fleet of taxis took theparticipants the short drive to theCambridge University Pressbookshop in the centre ofCambridge. It should have been ashort drive, but at least one taxiwas sufficiently unfamiliar withCambridge that they went to thePress Building on the other side oftown. Here we were treated to agenerous reception from the Press,and were able to purchase booksat 20% of list price. Mostparticipants managed to walk backto New Hall for dinner. By theend of dinner the storm cloudswere retreating and Jon Shanklintook all those that were interestedover to the UniversityObservatory, a 20 minute walkfrom New Hall. Here we wereable to use 20x80 binoculars toobserve comet Lynn, theThorrowgood refractor to observecomet 10P/Tempel 2 and theNorthumberland refractor for avariety of deep sky objects. Thetwo refractors are historicinstruments, with theNorthumberland first being usedto observe comets over 150 yearsago. Skies were very transparentand most observers spottedfragments of 109P/Swift-Tuttleblazing through our atmosphere.Observing finished aroundmidnight, though we managed toloose at least a couple of observerson the walk back to New Hall.They were eventually retrievedand I stayed up till dawn at a darksky site observing Perseid meteorsand the other two comets visible inthe morning sky.

On Sunday morning theparticipants were free to exploreCambridge and discussionsresumed after lunch. KayWilliams introduced the legendaryBritish observer, George Alcock.By way of background sherevealed that her son Gareth hadwanted to be an astronomer fromthe age of seven and hadeventually gone to Cambridge,MA to work with Brian Marsden.At a dinner party Nancy Marsden

had suggested that her next workshould be a biography of GeorgeAlcock. She was a bit daunted bythis as all her previous subjectshad been dead! George’s workspeaks for itself and includeshistory, architecture, ornithology,meteorology and astronomy aswell as a lifetime in teaching.George is perhaps most famousfor his comet and novaediscoveries, but some of his cometdrawings were also on display.George said a few words inresponse and sat down to astanding ovation.

George Alcock, Brian Marsden and JohnAlcock.

George was followed by anothercomet discoverer, KesaoTakamizawa, who had beenobserving comets, variable stars,novae, supernovae etc since the1960s. He now uses a 10-cm f4astrograph, with limitingmagnitude 15.5 (B) on T-Max 400and a 25-cm f2.8 Baker-Schmidtwith limiting magnitude 17. Hesometimes visits a 1500-m altitudesite in the mountains. He searchesin 720 areas and checks forvariable stars and minor planetsusing a PC. Over 5 years he hasobserved on 367 occasions, taken16530 shots and discovered twocomets, two novae, one supernovaand 502 new variables. Hechanged from visual tophotographic search techniques in1994.

Jean-Claude Merlin spoke abouthis work at Le Creusot, IAUstation 504, which has a 40-cm f5reflector and CCD, with more than120 clear nights a year. Heaverages 6 runs per month, takingtwo hours per run while observingtwo - five comets, with up to 30second exposures. He hasmeasured 900 positions since1997, with an average accuracy ofabout 0.5". As a guide hesuggested that Exposure time =pixel size/object speed. As anexample if pixel size was 2" andthe object was moving 30" perhour it would require a total of 4minutes exposure. Looking at

combined observations he hadfound systematic trends in theposition residuals, for example104P/Kowal 2 showed about a160 day period.73P/Schwassmann-Wachmann 3showed larger residuals thanaverage and he thought theremight be a 75 day period to them.Questions suggested that thesemight be related to poor orbitaldeterminations, or that the non-gravitational parameters didn'tquite match reality. However thepossibility of a true physicalphenomenon is not completelyruled out (for example precessioneffect on a small nucleus, such asin the case of comet 104P/Kowal2).

Bob Neville gave a veryenthusiastic talk about the need touse CCD equipment to makepositional measurements. His ownset-up at 967 Greens Norton wasentirely homemade. He used a 30-cm guide scope to a 22-cmreflector with a Starlight XpressSX CCD. The system allowed foroffset guidance to about 1 degree.The telescope had a roller drive inRA, which was very smooth andgave symmetrical star images. Forreduction he used Astrometricaand the USNO catalogue whichgives dense coverage, with Guide6 or Megastar for finder charts.ACLOCK (share/freeware)provided LST. Observers need touse short exposures to avoidsaturation. Sometimes poorseeing can actually help as itfuzzes out images; it is possible tomake worthwhile observationseven in poor environments.Nicolas Biver commented thatspeedy astrometry to provide goodorbits is essential to helpprofessionals target radiotelescopes.

During the break for tea we had agroup photograph and managed tocapture 11 discoverers on film,namely: George Alcock, DougBiesecker (SOHO), KazimierisCernis, Alan Hale, Michael Jager,Bill Liller, Don Machholz, DavidSeargent, Patrick Stonehouse,Kesao Takamizawa and KeithTritton who between them haddiscovered 28 comets and manySOHO comets. Research in Sky& Tel showed that sevendiscoverers who at that time haddiscovered 15 comets had beenpresent at an RTM meeting in1990 [David Levy (6), JeanMueller (1), Don Machholz (4),Clyde Tombaugh (1?), William



Sorrels (1), Doug Berger (1) andJeff Phinney (1)].

Before we resumed the formalsessions Charles Morris tookcentre stage and confessed that itwas time to honour his bet withAlan Hale that his comet wouldn’tbecome brighter than 0 mag. Itdid, so Alan received 10 onedollar bills. Our first speaker aftertea was Doug Biesecker, amember of the SOHO LASCOteam, which has discovered a largenumber of sungrazing cometfragments. They are all remains ofa single progenitor, which had aperiod of around 800 years, with ahighly inclined orbit (andtherefore not affected much byJupiter). The date of the originalprogenitor is not known andmultiple fragmentation hasoccurred. The most famousmember of the familly is Ikeya-Seki.

SOHO orbits at the L1 Lagrangianpoint between the earth and sun.The LASCO C2 camera has anorange filter with a bandwith of100nm and views the region from2.5 to 6 solar radii with aresolution of 13”. The C3 camerahas an orange/clear filter with abandwith of 300nm and viewsfrom 4 to 30 solar radii with aresolution of 56”. They offer 360deg coverage round the sun, withC3 taking about 1 frame an hourand C2 2 frames an hour. Thecamera support pylon hides thetrack of typical sungrazersbetween March and April. BeforeLASCO about 10 sungrazers hadbeen discovered from the groundbetween –371 and 1970. Six werediscovered by Solwind between1979 and 1984 and 10 by SMMbetween 1980 and 1989. SOHOhas now discovered 78 comets(updated to 79 that evening); itfinds about 1.9 comets a month,when corrected for the duty cycle.Of a subset of 53 Kreutz groupcomets, 33 were seen in C2 and 52in C3. It has not been possible tocompute an orbit for SOHO-45,though an mpeg loop shown laterclearly showed the object. Therewas some speculation as towhether the object was asungrazer or earth approacher.The team are getting better atvisual detection, but are stillrunning the automated searchprogram. This will only detectpotential Kreutz group members,so there could be other faintcomets being missed. The cometsshow fairly slow motion, and‘disc’ like ones are difficult to

spot, and may only be seen in afew frames.

Most of the comets brighten as 10log r, but after a certain point fadequickly. Magnitude scales are notwell calibrated on SOHO, partlybecause solar physicists requireless accuracy than cometobservers do. There is a problemwith vignetting and this makesreduction of the C2 and C3magnitudes uncertain. At T-20hours the median magnitude isaround 8, with the brightest 1st

magnitude and the faintest 10th.Most stop brightening 6 – 12hours before perihelion, whichimplies a fairly narrow range ofsizes. No comets have shown tailfeatures, and none have beenobserved closer than 3 solar radii.

The SOHO spectrometer hadobserved two comets. Lymanalpha emissions give an upperlimit to the solar wind velocity of640 km/sec. The comets suffer a20 kg/sec mass loss. A body 6.7-m in diameter would weigh120,000 kg and evaporate in about5 hours.

Brian G. Marsden, (Harvard-Smithonian Center forAstrophysics) provided a synopsisof his talk on 'Discoveries,astrometry, catalogues andawards'.

This month we are celebrating thefortieth anniversary of GeorgeAlcock's discovery of what wereannounced on the IAU Circulars atthe time as "Comet Alcock(1959e)" and "Comet Alcock(1959f)". Following the tradition,the year/letter designationssupplied in order of discoveryannouncement were later changedto 1959 IV and 1959 VI, showingthe order of passage of the year'scomets through perihelion. Interms of the new systemintroduced in 1994 theannouncements would haveinvolved the single appellations"Comet C/1959 Q1 (Alcock)" and"Comet C/1959 Q2 (Alcock)", the1 and 2 indicating the order ofannouncement of discoveries inhalf-month "Q" of the year, i.e.,the second half of August.Although we intended nodisrespect, some astronomers havebeen condemning the IAUCirculars for this "new" procedureof placing the name of thediscoverer, rather than thedesignation, in parentheses. As ithappens, this procedure is not newat all--early IAU Circulars speak

of "Comet 1922c (Baade)", forexample--and since "CometAlcock" is not by itself a uniqueform of address, it is surely morelogical to state the uniquedesignator for the comet first,backing it up with the additionalinformation identifying thediscoverer. The parenthetical useof the discoverer's name was formany decades also standard use inthe Astronomische Nachrichten,the principal international sourcefor information about discoveries,astrometry and orbits of cometsprior to the first IAU Circular.The discoverer's name, andsometimes also the date ofdiscovery, were specified in thisway, even in cases when theyear/letter designations were notused and the Roman numeraldesignations had not yet beensupplied. "Comet 1889 ...(Barnard 1888 Sept. 2)", alreadyrecognizing the year in which theobject would pass perihelion,uniquely defined the comet thatlater became 1889 I, that was fromthe start defined in somepublications as 1888e, and that wenow know as C/1888 R1(Barnard).

Since two earlier speakers haveprovided admirable accounts oftheir astrometric activities, there islittle I need add, except perhaps topoint out that it was not alwaysthis way. Modern CCDastrometry has turned out to be amuch more automatic, accurate,reliable, rapid and straightforwardprocess than the older astrometricprocesses involving photographyand micrometry.

Although I am happy to announcethat the thirteenth edition of theCentral Bureau for AstronomicalTelegrams/Minor Planet Center"Catalogue of Cometary Orbits"has just now become available, Iagain want to stress that by far thebest and most detailed suchcatalogue ever published is that byGalle of 1894, which has the soledisadvantage that it is just verymuch out of date! One feature ofthe 1894 catalogue is that itdefined the 15 multiple-apparitioncomets as (H) = Halley, (E) =Encke, ..., (Wo) = Wolf, (Fi) =Finlay. Actually, these periodiccomets are the only named objectsin the catalogue. Since there arenow 140 such comets, it mighthave been preferable if Galle hadinstead given them consecutivenumbers. The 1994 designationsystem has taken care of this bycalling them 1P, 2P, etc. As many

1999 October 15


as 55 comets were discoveredduring the twelve monthspreceding the end of July 1999.Although 22 and 14 of these werediscovered by the very automatedLINEAR and SOHO projects,respectively, even the remainingactivity was prodigious incomparison with a year as recentas 1971, which yielded only asingle discovery. Cataloguingnew discoveries has beencomplicated by the fact that, moreoften than not, LINEAR does notrecognize its discoveries ascometary. The same is also true ofother CCD discovery programs,which often involve exposuressufficient only to detect movingobjects. Cometary status is oftenestablished only by carefulscrutiny of objects that have orbitssuggesting cometary nature.Although some of these objects,like P/1999 DN3 (Korlevic-Juric),had already received designationsas minor planets, the beauty of thenew system is that suchdesignations can be retained andcombined with genuine cometarydesignations in a transparentmanner. Again to complicatematters, June 1999 saw for thefirst time the discovery of anobject (two objects, in fact) havinga retrograde orbit but no trace ofcometary activity!

While monetary prizes and otherawards specifically for thediscoveries of comets date back tothe year 1831, there was no suchinternational award between the1950s and this past year. TheEdgar Wilson Award, madepossible by a bequest from abusinessman in Kentucky, hasrecently been instituted forcometary discoveries by amateurastronomers (or individuals actingin an amateur capacity) for whomthose comets are named and whoare using for the discoveriesamateur, privately-ownedequipment. The amount availableeach year, roughly $20 000, isshared according to the number ofcomets with eligible discoveriesduring the year, which for thispurpose is taken as beginning at 0hours UT on June 11. The firstyear of operation has just ended,and there were six eligible comets,including the aforementionedP/1999 DN3 (with the twoCroatian CCD discoverers havingan equal share), a CCD discoveryin Arizona, a photographicdiscovery in Austria and threevisual discoveries in Australia.

My notes show a few furtherasides, which Brian mentioned inpassing. The D/ designation forsome periodic comets impliesdefunct or comets which JPLshouldn't send a mission to as theymight not find it. He would like tosee the numeric sequencedisappearing from the namedperiodic comets (eg S-L 1 to 9).Orbital computations are now notquite good enough to fit all theavailable observations, even withthe inclusion of non-gravitationalforces, and an improved model isclearly needed. July and August isthe rainy season in New Mexico,so there are not many LINEARobservations at this time of year.LINEAR doesn't follow objectsfrom night to night, which givesthe amateur the chance to do twonight linkages. By definitiontailed asteroids are comets (eg133P/Elst-Pizzarro). The EdgarWilson award begins on June 11th

because his brother died on June10th. The original bequestincluded recoveries, however thiswas thought to be unfair forrecoveries with well-known orbits,though accidental recoveriesmight count towards futureawards.

Responding to a question, Briansaid that comets are not allocateda provisional designation untilpositions were available. Severalrecent SOHO comets have yet tohave their positions measured andso do not yet have designations,and one has positions but noderivable orbit, despite clearlyexisting. Brian's talk continuedinto a panel discussion alsoincluding Doug Biesecker, BillLiller and Alan Hale. Kuiper beltobjects are cometary objects.There might be some brightKreutz group comets to come, buthe wasn't sure about different sub-groups. The IAU could decline toname a comet if this might causeaggravation. The first Solwindobject had been named, and theteam's intention had been to nameeach subsequent object with thenext three team-member's names,however they were instead namedafter the instrument. Newspacecraft missions planned forthe future include stereo solarimaging and all sky imaging downto 12th magnitude every 90minutes. The first named comet is1760 A1 as this was the year theMessier first began deliberatecomet hunting.

Guiseppe Canonaco commentedthat useful positional data had

been found in the logbook of aDutch ship, enabling an orbit to becomputed for a comet for the firsttime. Jon Shanklin noted that hehad been forwarded recentmeteorological logbook entriesrelating to comets Hyakutake andHale-Bopp, which showed thatmariners were generally unawareof the comets despite widespreadinformation being available andthat they only spotted them whenthey reached 2nd or 3rd magnitude.

The skies again cleared afterdinner, giving another verytransparent night (for Cambridge),with the Milky Way clearly visiblefrom the University Observatory.It was possible to observe cometsLynn and 10P/Tempel 2 and morefragments of 109P/Swift-Tuttlewere seen.

Monday began with the finalsession, which was devoted toshort presentations and posters.Philippe Morel of the SocieteAstronomique de France describedthe history of the comet section ofthe SAF. L'Astronmie, the Journalof the SAF had publishedobservations of comets since 1887when it was founded by CamilleFlammarion. Charles Bertaudformed the comet section in 1970.Annie Chantal LevasseurRegourd, who organised severaltraining camps for theInternational Halley Watch,followed him. Serge Thebaulttook over in 1989 and heorganised further camps toobserve comet Austin in Provencein 1990 and Hale-Bopp inNormandy in 1997. There areabout 120 members distributedthrough France and othercountries, of which around 15regularly submit observations,including drawings andphotographs. The Internet is veryimportant for communicationbetween members. Two membershave been successful indiscovering comets: Alain Maury(1998 X1) and Michel Meunier(1997 J2). Future projects includetranscribing old observations fromL'Astronomie. The SAF webpages (http://www.iap.fr/saf)include a section on comets.Visitors to Paris can be assured ofa welcome at 3 Rue Beethoven,across the Seine from the TourEiffel.

Stephane Garro went on toelaborate about the SAF cometdatabase. They had decided to usedatabase software and set up aform input so that those not



familiar with the ICQ codes couldenter observations correctly. Thefirst observations were from 1882,but there are few in the ICQdatabase prior to 1980 and theywere concentrating on enteringthese observations. There were713 observations between 1939and 1959. Many of the earlyobservations are rough, lackingsupporting data. Sometimes thedate is imprecise, for exampleonly quoting October 1901, othersgave no instrument and often onlythe date and magnitude werequoted.

Gyula Szabo described hisobservations at Konkoly innorthern Hungary. The 0.60-mSchmidt is now equipped with aCCD camera which has a 29'x18'field of view, compared to theoriginal plates which gave a 5°x5°field, however the CCD reaches22 magnitude compared to 19magnitude on film. He showedimages of 1998 K5, whichrevealed a bright tail, but littlecoma. Several comets showedfeatures in the coma. A shortperiod light curve of P/1998 U3over 2 hours showed variation inthe nuclear brightness. They hadcarried out surface photometryusing varying apertures,calculating the magnitude invarious rings. Theoretically (d lnB)/(d ln P) = -1 where P is theradius of the annulus and B itswidth. Some LINEAR comets, eg1998 K5, show much greaterslopes than this. Solar activity,diffusivity in the coma or activityin the comet may explain thevariation. Some of the data mayshow a trend, with minimumvalues occurring some 20 daysafter perihelion.

Bill Liller had followed cometHale-Bopp with his 0.20-m f1.5Schmidt with an ST5 CCD at theNewtonian focus on 338 nights.This gave a 27'x36' field at a scaleof 7" per pixel. He could get aphotometric accuracy of ±0.04magnitude using a broadband Vfilter (effectively minus IR).Looking at the inner coma only,there was a 20±5 day periodicitywhen the comet was inbound.After perihelion there wereongoing recurrent outbursts about100 days apart, which showed anoutflow of 40 - 55 ms-1.

After the tea break Bill Lillerpresented Jonathan Shanklin witha bottle of Chilean wine andthanked him for making all the

local arrangements for what hadbeen a very successful meeting.Bernd Brinkmann gave a shorttalk on his CCD observations withan SX camera on a C8 and withthe Askania 0.34/0.50-m Schmidtcamera and ST6 camera, whichalso has several smaller telescopeswhich are under used. Heprocesses the images, which aremostly 60-second exposures, withbias, dark and flat field frames anduses co-added frames for fainterobjects. He showed high qualityimages of several recent comets,which had been used forastrometry. He concluded withsome spectacular slides of Hale-Bopp.

Bill Liller and Michael Jager.

The final speaker was SimonaNikolova who spoke about theendurance lifetime of meter sizedcometary fragments. Meter sizedfragments were common in meteorstreams [though the audience wasa little sceptical that photographshad showed such objects prior toatmospheric entry] andfragmentation in comets wascommon. She had developed asublimation model, incollaboration with Martin Beech,using the interaction of solarradiation with water ice andseveral variable parameters. Sheconcluded that 2P/Encke looses0.65-m per revolution and a 10-meter sized fragment would lastaround 50 years; 55P/Tempel-Tuttle looses 0.18-m and afragment would last 1900 years.

During the meeting several posterswere on display, though I'm afraidI didn't have time to make detailednotes. The BAA Comet Sectionand TA had light curves of recentcomets on display, a selection ofsuperb comet drawings by GeorgeAlcock and the discoveryobservations of comet 1980 Y2 byRoy Panther. Comets Hyakutakeand Hale-Bopp featuredprominently in several posters.Nicolas Biver presented work onthe estimation of the rotationperiod of Hale-Bopp using visual

drawings. Philippe Moreldiscussed possible irregularities inHale-Bopp's rotation, illustratinghis poster with 15 drawings madethrough his 0.41-m Newtonian.Bill Liller had illustrations fromhis talk on Hale-Bopp and theBelgian VVS showed manyphotographs. Andreas Kammererdisplayed a comprehensiveanalysis of observations of the twocomets and this will also bedisplayed at the Meteor Sectionmeeting at the end of October.Simona Nikolova showed asynopsis of her talk on cometaryfragment lifetimes.

After lunch we boarded an air-conditioned coach for the trip toAvebury and Stonehenge. It isquite a long journey to Aveburyand I kept everyone entertainedwith descriptions of the passingscenery and was persuaded torecount some tales from my otherhobbies, which include churchbell-ringing, ice hockey, naturalhistory and cricket. Althoughthere was rain en route, it hadstopped by the time we reachedAvebury and there was time tolook round the large complex anddiscover its history in the localmuseum. After a light tea wecontinued on to Stonehenge,where we waited until the publichad left before being ushered intothe stone circle. We had an hourto ourselves and the lightingconditions provided a spectacularbackdrop to the ancientmonument, which is Britain'searliest astronomical observatory.The trip back was much quickerthan the outward journey and wearrived back before midnight.

Final goodbyes were said onTuesday morning and theremaining participants departedfrom New Hall for further touringround the UK and their journeyshome. During the three days ofthe Workshop 65 astronomers andfriends participated in what was avery rewarding meeting. Mythanks to all those that contributedto making it such a success and Ilook forward to the next one in afew years time.

Jonathan Shanklin

Thanks to Martin Mobberley forproviding the illustrations. Colourversions can be seen on his webpage athttp://ourworld.compuserve.com/homepages/MartinMobberley

1999 October 17


Observations of Comet 2P/Encke

Alex Vincent

During its 1994 apparition, I madean extensive number ofobservations of Comet Enckeduring the early evenings ofJanuary of that year. The cometwent through the Water Jarasterism of Aquarius and passedvery close to the star Pi Aquarii onJanuary 15.

I observed the comet throughDave Storey's 0.30-m telescope on1993 December 31 when itappeared as a faint ball shapedobject at 9.5 magnitude and alsoon 1994 January 16th near Pi

Aquarii shining at magnitude 8.5.It appeared slightly elongated asshown in the sketch. I tookseveral photographs of it at primefocus.

My other observations were donethrough 10x50 binoculars and an8x21 monocular on January 7th,13th, 14th, 16th, 17th, 19th, 23rd and28th. It appeared as a smallsmudge of light as it traversedAquarius

I took a number of photographs ofComet Encke with my camera

piggyback on the WorthingAstronomical Society's 0.30-mtelescope and also down at thebeach with a camera platform,using 50-mm, 135-mm and 270-mm lenses. As the moon wasaround on some of the days, thesky appears blue.

Comet Encke has the shortestknown period of any comet, whichis only 3.3 years, and its last returnwas in 1997, but it was notfavourable placed. It will howeverbe well placed for observation inthe year 2000.

C/1807 R1 (Great Comet)

Gary W. Kronk(Abridged from Cometography, to be published this winter by Cambridge University Press)

This comet was first seen on 1807September 9 by Castro Giovanni(Sicily). It passed perihelion onSeptember 19 and then emergedout of evening twilight, at whichpoint it became widely observed.Independent discoveries were thenreported by Jean Louis Pons(Marseille, France) on September21 and Edward Pigott (Bath) onSeptember 28. The comet passedclosest to Earth (0.1533 AU) onSeptember 26.

The comet was well observed asOctober began. William Dunbarsaw the comet on the 3rd. He wasthen situated about 5 milessoutheast of Natchez, Mississippi.He said it seemed similar inbrightness to a star of magnitude 2or 3, though "considerably larger."With a reflecting telescope (128x)he said the nucleus and coma wereshown "with tolerable distinctness;the idea produced in the mind ofthe observer, was that of a roundbody in combustion, which hadproduced so much smoke as toobscure the nucleus; the smokeseemed to be emitted in everydirection; but, as if it met on oneside with a gentle current of air,the smoke seemed to be repelledand bent around the nucleus,escaping on the opposite side, inthe direction of the tail." Dunbaradded that the telescope showedabout 63' of tail, while the nucleuswas considered one-third, orpossibly one-half, the brightnessof Mars. William Herschel sawthe comet with the naked eye onOctober 4. He said a reflector of

10-foot focal length showed anapparently round nucleus whichwas evenly illuminated across itssurface. Although he initiallyestimated its diameter as 5" in thereflector of 7-foot focal length,later in the observing session hesaid it was more like 3" across.He made several comparablenuclear diameter estimates duringthe next few days, and alsoestimated the tail length as 3.75degrees on October 18. On the19th Herschel said the comadiameter was 6 arcmin. Aboutmid October the Gentleman'sMagazine reported, "The Cometbecame visible immediately aftertwilight, at a considerableelevation in the heavens, nearlydue West, and set about onedegree half past eight o'clock,within a few degrees of N.W. Thenucleus, or star, when viewedthrough a small telescope,appeared about the size of a star ofthe first magnitude, but less vivid,and of a pale dusky colour. Theatmosphere of the Comet, owingto the limited power of thetelescope, was barely perceptible.The tail...appeared sometimesextremely brilliant, seeming to bea vibration of luminous particles,somewhat resembling the AuroraBorealis, and at other times almostto disappear." H. W. M. Olberssaw the comet on October 20 andsaid the comet exhibited two tailsseparated by about 1.5 degrees.The northern tail was very slender,faint, and straight, with a length ofabout 10 degrees, while thesouthern tail was short, wide, and

brighter, with a length of about 4.5degrees. The southern tail wasalso more intense on the southernside, while the concave side of thetail was very poorly defined.Olbers measured the very distinctnucleus as 8" or 9" across, whichhe said equalled about 900 miles.On October 24, Dunbar indicatedthe tail was about 2.7 degreeslong. On October 26, Herschelsaid the tail was "considerablylonger on the south-preceding,than on the north-following side."On October 28, Herschel said thetail's south-preceding side waswell defined, while the north-following side is shorter and"hazy." On October 31, Herschelsaid, "The tail continues to bebetter defined on the south-preceding than on the north-following side."

Moonlight interfered for about aweek before mid-November. Bythe 18th Dunbar said the comet hadvisibly diminished since earlierobservations, and noted thenucleus was about one-half itsobserved magnitude of October 3.On November 20, Herschel saidthe nucleus was distinctly visible,but only "a mere point" in the 7-foot focal length reflector. OnDecember 6, Herschel observedwith the 24-inch reflector anddescribed the coma as "a verylarge, brilliant, round nebula,suddenly much brighter in themiddle." It was about 4.75 arcminacross, with a tail 23 arcmin long.On December 7, Dunbar said, "Idirected the reflecting telescope to



the comet; the nucleus is nowmuch diminished in apparentmagnitude; I compared it with astar of the sixth magnitude in theSwan, which was within the fieldof view at the same time, theirapparent diameters were nearlyequal, but the comet is become sodim, as to be seen with the nakedeye only in a pure atmosphere,with favourablecircumstances...the coma is yetconsiderable, but the tail is nolonger visible...." On December16, Herschel said the cometresembled "a very bright, large,irregular, round nebula, verygradually much brighter in themiddle, with a faint nebulosity onthe south preceding side."

On 1808 January 1 Herscheldescribed the comet as "verybright, very large, very graduallymuch brighter in the middle." Headded that the 7-foot focal lengthtelescope showed the centerconsisting of very small stars, butthe 24-inch reflector showed"several small stars shiningthrough the nebulosity of thecoma." On January 6, Dunbarsaid the comet was no longervisible to the naked eye. Hisreflecting telescope showed thenucleus "as small as a star of theseventh magnitude." He added,

"the coma seems diminished morethan half of its appearance, on the6th of December [December 7thUT], and the nucleus is equallysurrounded by it on all sides,without any trace of tail, and sofaint as very much to resemblesome of the nebulae." On January14, Herschel described the cometas "bright, pretty large, irregularround, brighter in the middle." OnJanuary 16, Dunbar said, "In thegreat telescope, the coma is yetsufficiently conspicuous; thenucleus visible like a star of theeighth magnitude, in our purestatmosphere, and the coma littlechanged since the 5th instant[January 6th UT]."

On February 2, Herschel observedwith the 24-inch reflector anddescribed the comet as "verybright, large, irregular round, verygradually much brighter in themiddle." He added that a faint,diffused nebulosity was seen onthe north-preceding side, and hesurmised this might have been"the vanishing remains of thecomet's tail." On February 19,Herschel indicated the comet wasabout 3.4 arcmin across and"gradually brighter in the middle."He added, "The faint nebulosity inthe place where the tail used to be,still projects a little farther from

the center than in otherdirections." On February 21,Herschel noted the comet wasfainter than on the 19th, but stillabout the same size. It wasgradually brighter towards themiddle, and some nebulosity stillextended on the side where the tailonce existed. On February 24,Bessel observed the comet with a7-foot focal length reflector anddescribed it as very faint. OnFebruary 26, Dunbar "searchedwith great diligence and someanxiety, and at length found anobject which I had no doubt wasthe comet, situated between ChiCassiopeiae and OmicronCassiopeiae...." This observationwas made with the 6-footGregorian reflector, but the cometwas not detected in its finder.

The comet was last detected onMarch 27.87, when VincentWisniewski (St. Petersburg, nowLeningrad, Soviet Union)estimated the position as RA=1h43m 13.83s, DEC=+48d 54m38.6s.

Bessel ultimately used positionsreported from September 22 toMarch 27 and found the cometwas moving in a long-period orbitof nearly 2000 years.

Comet Prospects for 2000

The year 2000 is not a particularlygood one for predicted returns ofperiodic comets. The cometpredicted to be brightest is a newdiscovery by LINEAR, 1999 S4.There is a good chance that itcould become a naked eye objectin the northern sky next summer.A couple of long period cometsdiscovered in previous years arestill faintly visible and there aresome poor returns of short periodcomets. Recent theories on thestructure of comets suggest thatany comet could fragment at anytime, so it is worth keeping an eyeon some of the fainter periodiccomets, which are often ignored.Ephemerides for new andcurrently observable comets arepublished in the Circulars, CometSection Newsletters and on theSection, CBAT and SeiichiYoshida's web pages. Completeephemerides and magnitudeparameters for all cometspredicted to be brighter than about18m are given in the InternationalComet Quarterly Handbook

1;

details of subscription to the ICQare available from the comet

section Director. The sectionbooklet on comet observing2 isavailable from the BAA office orthe Director; a new edition islikely to be printed in 2000.

First some comets, which were atperihelion in previous years.Comet Hale-Bopp (1995 O1), thegreat comet of 1997, is still fadingslowly and could be 13m at thebeginning of the year, though thisis likely to be the last year withvisual observations. It is onlyobservable from SouthernHemisphere locations as it loopsround Mensa.

1999 S4 (LINEAR) offers theprospect of a naked eye cometnext July. The comet shouldbecome visible to large aperturetelescopes in the New Year,possibly earlier if the comet isbrighter visually than with CCD.It brightens slowly, but also closeswith the Sun and reachesconjunction in March. We shouldpick it up again as a binocularobject in the northern sky in June,becoming naked eye in July. It

doesn't stray far from the Sun andthen begins to head south andback towards conjunction. UKobservers will loose it by August,but Southern Hemisphereobservers may follow it intoSeptember and will pick it upagain as a telescopic object inNovember.

Stop Press: Another new comet1999 T1 (McNaught-Hartley)may reach binocular brightness inDecember 2000. More details inthe next issue.

141P/Machholz 2 (1999 P1) wasrecovered by Rob McNaught inearly August, not far from itspredicted track. Its likelybrightness is still uncertain, but itcould be fading from 8th

magnitude at the end of 1999.

29P/Schwassmann-Wachmann 1is an annual comet which hasfrequent outbursts and seems to bemore often active than not at themoment, though it rarely getsbrighter than 12m. In the first halfof 1999 it was in outburst on

1999 October 19


several occasions. The randomlyspaced outbursts may be due to athermal heat wave propagatinginto the nucleus and triggeringsublimation of CO inside thecomet. It begins the year inScorpius and reaches opposition inthe same constellation in June. Itpasses through Ophiuchus and intoSagittarius and is in solarconjunction in December. Thiscomet is an ideal target for thoseequipped with CCDs and it shouldbe observed at every opportunity.Unfortunately opportunities forUK observers may be limited, asits altitude does not exceed 11°from this country.

This year sees comet 2P/Encke's58th observed return to perihelionsince its discovery by Mechain in1786. The orbit is quite stable,and with a period of 3.3 yearsapparitions repeat on a 10 yearcycle. This year the comet is notparticular well seen, but there areshort observing windows from theNorthern Hemisphere prior toperihelion, which is in September,and in the Southern Hemisphereafter the comet reaches perihelion.There is some evidence for asecular fading and anyobservations will help confirmthis. Another suggestion is thatEncke has two active regions, anold one with declining activity,which operates prior to perihelionand a recently activated onepresent after perihelion. Thecomet is the progenitor of theTaurid meteor complex and maybe associated with several Apolloasteroids.

9P/Tempel 1 was first observed in1867, but was lost between 1879and 1967 following an encounterwith Jupiter in 1881 whichincreased the perihelion distancefrom 1.8 to 2.1 AU. Furtherencounters in 1941 and 1953 put qback to 1.5 AU and calculationsby Brian Marsden allowedElizabeth Roemer to recover it in1967. Alternate returns arefavourable, but pertubations willonce again increase the periheliondistance in the middle of the nextcentury. This return is anunfavourable one, but SouthernHemisphere observers will be ableto follow it as it fades afterperihelion. It is an importantcomet to observe as it is apotential spacecraft target, so allobservations will be welcome.

A few comets not due to returnuntil 2001 may become visibletowards the end of the year.

Horace Tuttle was the firstdiscoverer of 41P/Tuttle-Giacobini-Kresak in 1858, whenhe found a faint comet in LeoMinor. Nearly 50 years later,Professor M Giacobini discovereda 13th magnitude object whilstcomet hunting, which wasobserved for a fortnight. A C DCrommelin linked the apparitionsin 1928 and made predictions forfuture returns, but the cometwasn't recovered and it was givenup as lost. In 1951, Lubor Kresakdiscovered a 10th magnitude cometin 25x100 binoculars whilstparticipating in the Skalnate PlesoObservatory's program of routinesearches for comets. After furtherobservations the comet wasidentified with the lost comet anda better orbit computed. At the1973 return, which was similar tothe 1907 return, it underwent amajor outburst and reached 4th

magnitude, before fading and thenundergoing a second outburst.Alternate returns are unfavourableand this is one of them, but thecomet has been observed at a fewof them and it should be possibleto observe it from equatorialregions in December. If itundergoes a further outburst, morewidespread observation may bepossible.

47P/Ashbrook-Jackson wasdiscovered in 1948 following anapproach to Jupiter in 1945, whichreduced the perihelion distancefrom 3.8 to 2.3 AU. Althoughintrinsically relatively bright, thelarge perihelion distance keeps itfaint. Alternate returns arefavourable, but this is not one ofthem, although the comet will bereasonably well placed forSouthern Hemisphere observers at13th magnitude.

Professor A Schwassmann and AA Wachmann of HamburgObservatory discovered their 3rdperiodic comet, on minor planetpatrol plates taken on 1930 May 2.Initially of magnitude 9.5 itbrightened to nearly 6m, thanks toa very close approach to Earth(0.062 AU) on June 1. The initialorbit was a little uncertain and thecomet wasn’t found at this orsucceeding apparitions until 1979.The comet passed within 0.9 AUof Jupiter in 1953, and 0.25 AU in1965. In August 1979, MichaelCandy reported the discovery of acomet on a plate taken by JJohnston and M Buhagiar whilesearching for minor planets; thishad the motion expected for73P/Schwassmann-Wachmann

3, but with perihelion 34 days laterthan in a prediction by BrianMarsden. Missed again at the nextreturn, it has been seen at the lastthree returns. The 1930 approachto Earth is 9th on the list of welldetermined cometary approachesto our planet. In May 2006 it willmake another close approach(0.082 AU), when it could againreach 7m or brighter. This smallmiss distance makes it aconvenient spacecraft target, andthe Contour mission is scheduledto intercept it, as well as comets2P/Encke and 6P/d’Arrest andpossibly a new discovery.Following its outburst in 1995,73P/Schwassmann-Wachmann 3 isexpected to show fresh cometarysurfaces, whilst 2P/Encke is an oldcomet and 6P/d’Arrest an averageone. With the orbit approachingso closely to the Earth, anassociated meteor shower mightbe expected, and the comet hasbeen linked to the Tau Herculidshower, though the radiant nowlies in the Bootes - Serpens region.Strong activity was reported in1930 by a lone Japanese observer,but little has been seen since then.It is likely that any future activitywould be in the form of a short-lived outburst, confined to yearswhen the comet is at perihelion.

The comet underwent severaloutbursts at its last return,reaching naked eye brightness andthe expected magnitude at thisreturn is uncertain. The cometwill be brightening towards theend of the year on its way toperihelion in late January 2001. Ifit maintains the level of activityseen at the last return it might beglimpsed in the morning skyaround the beginning of Decemberand may reach 7th magnitude at theend of the year, although the solarelongation is not good.

A number of fainter comets maybe of interest to CCD observers orthose with large aperturetelescopes. These include:Spacewatch (1997 BA6) (slowlyfading from 13tm in January),LINEAR (1999 H3) (fading from13m in January), LINEAR (1999L3) (fading from 13m in January),LINEAR (1999 K5) (14tm betweenMay and September), LINEAR(1999 T2) (13m in late Summer)and 95P/Chiron (16m at oppositionin late May in Libra).Ephemerides for these can befound on the CBAT WWW pages.CCD V magnitudes of Chironwould be of particular interest as



observations show that its absolutemagnitude varies erratically.

Several other comets return toperihelion during 2000, howeverthey are unlikely to become brightenough to observe or are poorlyplaced. 71P/Clark, 76P/West-Kohoutek-Ikemura, 64P/Swift-Gehrels, 108P/Ciffreo,112P/Urata-Niijima,137P/Shoemaker-Levy 2 andP/Lovas 2 (1986 W1) haveunfavorable returns. 14P/Wolf,17P/Holmes, 33P/Daniel,70P/Kojima, 87P/Bus,114P/Wiseman-Skiff, D/Kowal-Mrkos (1984 H1), D/Shoemaker 2(1984 W1), P/Shoemaker-Levy 5

(1991 T1), Skiff (1999 J2),LINEAR (1999 K5), LINEAR(1999 K8) and LINEAR (1999N4) are intrinsically faint ordistant comets. 5D/Brorsen hasnot been seen for over a centuryand is unlikely to be recovered,however if it still exists andresumes activity it could be abinocular object in the dawn skybetween late August and earlyOctober, however it could bevirtually anywhere along itsorbital track.

Looking ahead, 2001 seesfavourable returns of comets19P/Borelly, which may reach 9th

magnitude and 24P/Schaumasse,which may reach 10th magnitude.

References and sources

1. Nakano, S. and Green D. W.E., Eds, International CometQuarterly 2000 Comet Handbook,(1999).2. Shanklin, J. D., ObservingGuide to Comets, (1996).3. Marsden, B. G. Catalogue ofCometary Orbits, 13th edition,IAU CBAT, (1999).4. Kronk, G. W., Cometographia,Cambridge University Press,(1999).

Jonathan Shanklin

Comets reaching perihelion in 2000

Comet T q P N H1 K19P/Tempel 1 Jan 02.6 1.50 5.51 9 5.2 23.4C/LINEAR (1999 L3) Jan 04.8 1.99 10.0 10.0114P/Wiseman-Skiff Jan 11.7 1.57 6.66 2 11.5 15.0137P/Shoemaker-Levy 2 Feb 05.8 1.87 9.37 1 14.5 10.0112P/Urata-Niijima Mar 04.4 1.46 6.65 2 14.0 15.0 P/Lovas 2 (1986 W1) Mar 11.7 1.45 6.75 1 10.0 10.0 C/Skiff (1999 J2) Apr 05.9 7.11 6.4 5.0108P/Ciffreo Apr 18.4 1.71 7.24 2 9.2 15.0 64P/Swift-Gehrels Apr 21.9 1.34 9.18 4 9.0 20.0 C/LINEAR (1999 K8) Apr 24.4 4.20 1.9 15.0 C/LINEAR (1999 N4) May 25.5 5.50 6.0 10.0 17P/Holmes May 11.8 2.17 7.07 8 10.0 15.0 76P/West-Kohoutek-Ikemura Jun 01.3 1.60 6.45 4 11.0 15.0 D/Shoemaker 2 (1984 W1) Jun 15.5 1.32 7.84 1 13.0 10.0 33P/Daniel Jun 23.5 2.16 8.07 8 10.5 20.0 C/LINEAR (1999 K5) Jul 04.6 3.25 6.0 10.0 C/LINEAR (1999 S4) Jul 24.4 0.75 7.0 10.0 P/Shoemaker-Levy 5 (1991 T1) Aug 18.6 1.99 8.68 1 13.0 10.0 2P/Encke Sep 09.7 0.34 3.30 57 10.0 8.8 70P/Kojima Sep 14.8 2.00 7.05 4 11.0 15.0 5D/Brorsen Oct 05± 0.54 5.5± 5 9.5 10.0 D/Kowal-Mrkos (1984 H1) Oct 26.8 2.68 9.31 1 12.0 15.0 14P/Wolf Nov 21.1 2.41 8.21 14 5.3 30.0 C/LINEAR (1999 T2) Nov 24.7 3.02 6.0 10.0 71P/Clark Dec 01.9 1.56 5.51 5 8.6 15.0 C/McNaught-Hartley (1999 T1) Dec 09.6 1.15 5.0 10.0 87P/Bus Dec 29.8 2.18 6.51 3 10.0 15.0

The date of perihelion (T), perihelion distance (q), period (P), the number of previously observed returns (N) and themagnitude parameters H1 and K1 are given for each comet. Note: m1 = H1 + 5.0 * log(d) + K1 * log(r)

1999 October 21


the comet s talejds/tail12b.pdf · issue the iwca was very successful and an enjoyable time was had...

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