author of uranometria (5) introduction to astrophotography · 2012-05-30 · sk what's the...

AAS Journal 24 April 2008

The solutions to the March crossword are on page 7.

Southern Sentinel Crossword April 2008 Edition

Across

1 A common slang term for a large aper-

ture telescope (5,6)

5 Australian Astronomy Magazine (3,3,5)

6 Nearby star located in Ophiuchus (8,4)

11 Apparent backward motion of outer

planets (10)

13 Constellation starting with 'L' (5)

Down

2 Energy found between radio and the

visual spectrums (8)

3 Author of Uranometria (5)

4 Constellation starting with 'C' (5,5)

7 Bright and Orange this star rises in

Autumn (8)

8 The constellation 'The Triangle' (10)

9 Where is the Jet Propulsion Laboratory

located? (8)

10 Constellation starting with 'P' (6)

12 Moon of Saturn with an atmosphere (5)

1 2 3 4

5

6 7 8 9

10

11 12

13

Visit our web site: www.astronomy.org.nz

SOCIETY JOURNAL

April 2008

Henk Stolk will talk about what to buy, how to prepare, how to plan and how to get the best out

of your images

Introduction to Astrophotography


President: Henk Stolk 0274 878655

Vice President: John White 486-2398

Treasurer: Helen McRae 021 494418

Secretary: Jennie McCormick 576-9815

Curator of Instruments: Ivan Vazey 535-3987

Librarian: Olga Brochner 625-9444

Editor:

Councillor: Mark Cannell 520-1123

Councillor: Andrew Goodfellow 524-4369

Councillor/Webmaster: Nick Moore 537-1500

THE SOCIETY COUNCIL

JOURNAL OF THE

AUCKLAND ASTRONOMICAL SOCIETY

The aim of this publication is to promote and foster the science of astronomy, and to encourage the association of astronomical observers and other persons interested in astronomy.

11 issues per year.

Auckland Astronomical Society, Inc.,

P O Box 24-187 Royal Oak, Auckland 1345, New Zealand

Email : [email protected]

Internet : www.astronomy.org.nz

Contact Us :

April 2008 23 AAS Journal

M20 region in Sagittarius by Kenric Ma, winner of the 2008 Harry Williams Trophy

The moon

imaged by

Prasad De

Zoysa, win-

ning image in

the Solar Sys-

tem Section


In the first instants of the Big Bang, micro-scopic quantum fluctua-tions — little, random irregularities that got inflated to become the seeds of cosmic struc-ture today — indeed seem to have been ran-dom at all scales, as inflation predicts — rather than being shaped or directed by some additional process. However, there are sev-eral hints of something else going on right at the current edge of uncer-

tainty.

Some versions of cos-mic inflation itself are now eliminated. Others have gained new support. (For you cosmo-geeks in the know: the "scalar spectral index" seems to be clearly tilted, with a value around 0.96 instead of 1.0.) "The new WMAP data rule out many mainstream ideas that seek to describe the growth burst in the early universe," explains WMAP principal investigator Charles Bennett (Johns Hopkins University). "It is astonishing that bold predictions of events in the first

moments of the universe now can be confronted with solid measurements."

WMAP also finds concrete evidence for a "cosmic neutrino background" filling space. The neutrinos (weak, extremely low-mass particles) came from nuclear reactions in the dense matter that filled the universe in the Big Bang's first few minutes. By the time of the visible microwave background, 380,000 years later, neutrinos still amounted to 10% of all matter and energy in the universe, compared to their vanishingly small proportion today. In addition, the three types of neutrinos that exist have masses that can add up to

no more that 0.61 electron volt, agreeing with laboratory experiments.

The cosmic "dark ages" — the era between when the Big Bang cooled and the first stars formed (an era when the universe became so cold that molecular-hydrogen snowflakes may have formed) — began ending around cosmic age 400 million years (redshift 11). This change is known as the "reionization era." The date fits in with evidence that's been coming from more normal astronomical methods. (Reionization apparently was, how-

ever, a drawn-out affair, happening by fits and starts in different places.)

"We are living in an extraordinary time," says Gary Hinshaw (NASA/Goddard Space Flight Center). "Ours is the first generation in human history to make such detailed and

far-reaching measurements of our universe."

The first peak reveals a specific spot size for early universe sound

waves, just as the length of guitar string gives a specific note. The

second and third peaks are the harmonics.


MONDAY 14th APRIL 2008 8.00 PM AT THE EPSOM METHODIST CHURCH HALL

MONTHLY MEETING

Friends and visitors are welcome.

This talk will provide an introduction into astro-photography. We will discuss how to prepare,

what to buy, how to plan and how to do it.

There will also be a brief demonstration of the most essential software and how to turn your im-

ages into real professional pictures.

Introduction to Astrophotography

Or

How to beat Dave, Guy and Kenric next year at the Burbidge Dinner

Presented by Henk Stolk


Calendar of Society Events

April 2008 Fri 4 7.30pm Young Astronomers with Margaret Arthur

4-6 Waharau Dark Sky Weekend

Sun 6 3am Daylight Savings ends

Mon 14 8pm April Monthly Meeting—Astrophotography by Henk Stolk

Fri 18 7.30pm Night Eyes. “Alientology” by David Britten

Mon 21 8pm Annual General Meeting

Mon 28 8pm “Introduction to Astronomy” presented by Danut Ionescu

May 2008

Fri 2 7.30pm Young Astronomers with Margaret Arthur

Mon 12 8pm May Monthly Meeting

Fri 16 7.30pm Night Eyes with David Britten

23-25 RASNZ Annual Conference (Tekapo)

Mon 26 8.00pm Introduction to Astronomy

MEETING VENUE IS AT THE STARDOME AGAIN

New Members 2008

We welcome the following to the Auckland Astronomical Society: Antony Walford, Laurence Cochrane, Cy Holmes, Keith Russell and Sina Masoud-Ansari


cantly — and, as a result, yields new conclusions.

The following results combine the new WMAP data with other recent astronomical

clues:

The universe is 13.73 ± 0.12 billion years old. That's an uncertainty of only 0.9% now (at the 68-percent confidence level). Astronomy books in your public library probably

say the universe is "between 10 and 20" billion years old.

The Hubble constant, the rate of the universe's expansion today, is 70.1 ± 1.3 kilome-tres per second per mega-parsec. Books in your library probably say it's "between 50

and 100."

The sum total of everything in the universe consists of the following: matter made of atoms ("baryonic matter") 4.6% ± 0.15%, non-baryonic dark matter 23% ± 1%, dark energy 72% ± 1.5%. We know almost nothing about what the dark matter and dark energy are, but we do know quite well now how

much of each is out there.

All this matter and energy adds up, within just 1% uncertainty, to exactly enough to make space "flat," as inflationary-universe theories predict. That is, empty space on the largest cosmic scales is just like the ordinary space right around you: having no overall curvature or weird geometry. This also im-plies that space extends infinitely far beyond our visible horizon, equally in all directions, as best we

can tell.

The behavior of the mysterious dark energy is be-coming clearer. Its "equation of state," a parameter known as w, equals –1 to a precision of 6%. That's the best determination of it yet. This implies that dark energy is not something that spreads out as space expands, the way particles in space would, but is something inherent to space-time itself — so that one cubic centimetre of space always contains the same amount of it no matter how greatly space has expanded. This matches Albert Einstein's idea of a "cosmological constant" from the 1920s

(referred to by the Greek letter Lambda, Λ) and argues against the dark energy being a

sort of physical substance that has been proposed, dubbed "quintessence."

This also means that the universe's stars, planets, and atoms will not all be torn apart in the coming billions of years by a runaway increase in cosmic acceleration, a situation

called the Big Rip.

Relative constituents of the universe

today, and for when the universe was

380,000 years old, 13.7 billion years

ago. Neutrinos used to be a larger

fraction of the energy of the universe

than they are now.

Credit: WMAP Science Team


The New Era of High Precision Cosmology

From Sky & Telescope

A sk what's the greatest scientific triumph of our lifetime, and somewhere near the top of the list would be the establishment of "precision cosmology." In just the last decade or so, astronomers working in a remarkable specialty have deter-

mined — with high accuracy — such things as the date of the Big Bang, the amount and makeup of all the matter and energy in the universe, the large-scale shape of space, and how cosmic structure (galaxy clusters, galaxies, stars) grew and evolved from the very

beginning to now, and why.

Along the way, researchers have confirmed some key predictions of the "inflationary universe" theory of how the Big Bang itself erupted from a much larger, underlying pre-existence, which could be producing inconceivable numbers of other, separate big-bang

universes all the time.

This has become possible not by conventional astronomy, but by analyzing the cosmic microwave background radiation that covers the entire sky. This weak radio glow is liter-ally the white light emitted by the still-white-hot universe as it stood just 380,000 years after the Big Bang. The light has been redshifted down into the microwave part of the

spectrum (by a factor of 1,091) by the expansion of space since that time.

Dozens of experiments have mapped tiny, telltale irregularities in the microwave back-ground; these projects have worked at various scales and have pointed at different parts of the sky. But the most important instrument now doing this work is the orbiting Wilkin-son Microwave Anisotropy Probe (WMAP). It is mapping the background radiation's temperature and polarization across the entire celestial sphere, and at a wide variety of angular scales: from large (many degrees wide, constellation-size) to nearly as small as

the resolution of the human eye.

As time goes on, WMAP has continued to sharpen its picture.

Its first-year data release, in 2003, set milestones in precision cosmology -- among other things, pinning the age of the universe to 13.7 billion years with an uncertainty of just a couple percent, and confirming the existence of the recently discovered "dark energy"

that is making the expansion of the universe speed up.

The three-year data release, in 2006, confirmed that the first results were on target, re-fined the numbers, and put new constraints on how cosmic inflation could have worked

during the first 10–32 second or so of the Big Bang.

The New Big Picture

Just after we sent that issue to press, WMAP's science team released the much-awaited five-year data set, along with their conclusions about what it tells. Once again, the addi-tional data (and better long-term calibration of the instruments) refines the picture signifi-


Waharau Dates for 2008 Here are the Waharau dark sky dates for your 2008 diary.

Friday April 4th Friday July 4th

Friday September 26th

We hope to see you all there.

Society News

NIGHT EYES April Meeting

The April meeting of the Night Eyes junior group will be held at 7:30pm

on Friday 18 April in the Sun Room at the Observatory.

The main topic for the meeting will be:

"Alientology" Parents, friends and other Society members are also very welcome to attend.

For further information please contact David Britten:

[email protected] or ph. 846-3657

ANNUAL GENERAL MEETING Monday, 21 April 2008 at 7.30pm Auckland Stardome Observatory

One Tree Hill Domain

The agenda will include:

• presentation of reports

• election of officers and Council members

• general business

Light refreshments will be available after the meeting.


Waharau Dark Sky Weekend April 4-6, 2008

T he Auckland Astronomical Society has arranged another informal and fun astro-nomical get-together weekend at the Waharau Outdoor Education Centre, located

in the Waharau Regional Park 8km north of Kaiaua on the Firth of Thames.

These weekends are an ideal way for new and established members to meet each other, find out more about the different types of telescopes which many members bring to the

occasion, and learn about new aspects of the night sky and its wonders.

The centre includes a lodge, five chalets (88 bunks) and an ablution block. It is sur-rounded by native bush with bush walks and even glow-worms; there is a bird sanctuary on the coast just a short drive away, and the Miranda hot springs are a little further along the same road. There is a large, fully-equipped kitchen with walk-in 'fridge; bring your own food and drink, but tea, coffee and some biscuits for the long night watches are pro-vided. Incompetent cooks will find a hotel, fish and chip shop and dairy close enough to

prevent starvation. You will need to bring your own sleeping bag and pillow.

The contact person is Dave Moorhouse (email: [email protected]; mobile phone

0274 819-089) Bookings can be made online or by emailing (including inquiries) Dave.

Cost: $25 for two nights, $15 for just one. If you don't use the accommodation, it is just $10 per night. In case some emergency arises (there's never been one so far) people at-tending are required to register on arrival and sign out when leaving; they will also be expected to sign on for one of the clean-up tasks which inevitably have to be done in this

self-help environment.

You will need to bring:

• Sleeping bag and pillow.

• Crockery and cutlery are available on site, but cannot be guaranteed by A.A.S.

• Warm clothing / Toiletries.

• Food for breakfast / lunch / dinner.

• Telescope / Binoculars / camera and dew caps, if you have them?

• Torches – ONLY RED LIGHT PLEASE!! – It is important for quality viewing, to

have your eyes properly adjusted to the dark – white light will degrade this.

• Your Friendship

Park Rule : Sorry, no pets.

See you there!


cations.

Because Saturn has such a powerful gravitational grip on its moons, the mission team had assumed that Titan's spin axis is exactly perpendicular to its orbital plane and that the big moon rotates synchronously, completing exactly one rotation every time it goes around Saturn (15.945 days). But the radar data are telling a different story: Titan's spin axis has to be tipped slightly, just 0.3°, and its rotation needs to be ever-so-slightly faster than expected, by just 0.004%. Moreover, this slight rotational mismatch seems to be

increasing — Titan is speeding up!

(It's amazing to me that the radar maps and spacecraft tracking are precise enough to see

these discrepancies. But they're really real!)

One explanation might be that winds in Titan's massive atmosphere, which is much denser than Earth's, are slowly influencing the moon's rotation. Ordinarily this effect would be inconsequentially tiny. (For example, persistent seasonal winds in Earth's at-

mosphere change the length of our day by no more than a millisecond per year.)

But several years ago theorists surmised that Titan probably isn't solid throughout. In-stead, they argue, this Mercury-size moon has a global layer of ammonia-infused water just below its water-ice crust. A global ocean would effectively decouple the crust from rotation of the deeper interior, allowing the outer shell to spin at its own rate and making

it much more susceptible to external forces like surface winds.

In tomorrow's issue of Science, Ralph Lorenz (Applied Physics Laboratory) and eight others argue that an internal ocean is the best way to make sense of Titan's rotational quirks. "The bottom line," Lorenz told me via e-mail, is that "the rotation is changing,

and the only way it could be changing is if the crust is decoupled."

Right now it's late winter in Titan's northern hemisphere, and the leading circulation model predicts that near-surface winds should be causing the spin to accelerate. That's what Cassini has observed. In a few years, once northern summer arrives, the spin rate

should slow. Cassini should be able to track this reversal if can hold out until, say, 2011.

However, the model and Cassini's observations don't match exactly. Specifically, Titan seems to be about two years behind its predicted speed-up schedule. Perhaps the model needs tweaking, or other forces (such as Saturn's pull on a bulge in Titan's midsection) might be involved. Conceivably Titan's spin axis is wobbling, as has been suggested by French dynamicist Benoît Noyelles. It's even possible that Titan was spun up by a large impact in the recent past. But a strike that potent should only occur every 100 million

years — and it would have punched a hole in the ice at least 100 km across!


March 20, 2008

A mong the most anticipated results from NASA's Cassini mission was a chance to reveal the surface of Titan, Saturn's largest moon and arguably the most

fascinating solid body in the solar system (besides Earth, of course).

Cassini's first good chance to peer through Titan's murky atmosphere using radar came in October 2004. Those initial radar images revealed a world brimming with geologic

diversity:

But something strange came to light later on, after some of the same areas were viewed again on subsequent close passes: Titan's features weren't quite where they were sup-posed to be. In some cases they were nearly 20 miles (30 km) from their predicted lo-

What's Up with Titan's Spin?

Kelly Beatty, Sky & Telescope

If a subsurface ocean lies between Titan's crust and its deep interior, then winds in the

dense atmosphere might be forcing the moon to spin slightly faster during northern win-

ter (left) and to slow down during northern summer (right).

Christophe Sotin / Gabriel Tobie / Science magazine


Introductory Astronomy

Talking to Romanian Amateur

Astronomers about NZ

Astronomers and Societies

Presented by Danut

Ionescu

These informal meetings are designed for people with little or no observing experience, and those who wish to learn their way around the night sky. The sessions are interactive, so feel free to ask questions and generally join in. Also, bring along any “optical aids” you may have (binoculars or telescopes) and hopefully Auckland’s weather will be kind to us, and we can go outside and observe what we’ve been discussing!

SOLUTION TO THE MARCH CROSSWORD

Across: 5 Albireo, 6 Capella, 8 Mimas, 9 Orange, 10 Sunspot, 12 Averted Vision.

Down: 1 Serpens, 2 Charles Messier, 3 Avior, 4 Arc Second, 7 Sunset, 11 Orbit.


The Night Sky for April

Brian Loader RASNZ

April 4 2.5% lit crescent Moon 4.5° from Venus in the morning sky.

6 NZDT ends at 3 am NZDT = 2 am NZST.

New Moon at 3:55 pm NZST (03:55 UT).

8 Moon at perigee, its closest to the Earth for the Lunar month, 361085 km.

12 45% lit Moon 2° from Mars, magnitude 1.0, evening sky.

13 Moon at first quarter 6:32 am NZST (Apr 12, 18:32 UT).

15 77% lit Moon 3° from star Regulus at 7 pm, 1.25° at midnight, occultation

south and west of Australia.

Moon also 5.2° from Saturn (magnitude 0.5) at 7 pm, 3.6° at midnight.

16 Mercury at superior conjunction on far side of Sun.

19/20 99% lit Moon 6° from star Spica, magnitude 1.1, evening sky, 3° low to

west an hour before sunrise morning of 20th.

20 Full Moon at 10:25 am NZST (10:25 UT).

23 Moon at apogee, its greatest distance from the Earth for the Lunar month,

405946 km.

24 91% lit Moon occults the star Antares in morning sky. Disappearance at lit

limb, reappearance at unlit.

27 Mars 4.8° above Pollux in evening sky. Both with magnitude 1.2.

28 59% lit Moon 6° from Jupiter in morning sky.

29 Moon at last quarter 2:12 am NZST (Apr 28, 14:12 UT).

30 38% lit Moon less than 0.5° from Neptune, magnitude 7.9, in morning sky.

Occultation of Neptune visible from northern half of Australia.

From Brian Loader's monthly solar system notes on the RASNZ web site. Bookmark

Brian’s excellent site www.rasnz.org.nz for more detail and many useful links


team member Stephen Holland of Goddard. "If someone just happened to be looking at the right place at the right time, they saw the most distant object ever seen by human eyes

without optical aid."

Most gamma ray bursts occur when massive stars run out of nuclear fuel. Their cores collapse to form black holes or neutron stars, releasing an intense burst of high-energy gamma rays and ejecting particle jets that rip through space at nearly the speed of light. When the jets plow into surrounding interstellar clouds, they heat the gas to incandescent visibility. It is this gaseous "afterglow" which was visible to the human eye on March

19th.

GRB 080319B's afterglow was 2.5 million times more luminous than the most luminous supernova ever recorded, making it the most intrinsically bright object ever observed by humans in the universe. The most distant previous object that could have been seen by the naked eye is the nearby galaxy M33, a relatively short 2.9 million light-years from

Earth.

Analysis of GRB 080319B is just getting underway, so astronomers don't know why this burst and its afterglow were so bright. One possibility is the burst was more energetic than others, perhaps because of the mass, spin, or magnetic field of the progenitor star or its jet. Or perhaps it concentrated its energy in a narrow jet that was aimed directly at

Earth.

GRB 080319B was one of four bursts that Swift detected on March 19th, a Swift record for one day. Swift science team member Judith Racusin of Penn State University com-ments, "coincidentally, the passing of Arthur C. Clarke seems to have set the universe

ablaze with gamma ray bursts." A fitting farewell, indeed.

-from NASA press release

The afterglow of GRB 080319B as recorded by Swift's X-ray Telescope. Image on the left

is the x-ray image while the one on the right is from the UV telescope.


21 March 2008

M arch 21, 2008: A powerful gamma ray burst detected March 19th by NASA's Swift satellite has shattered the record for the most distant object that could be

seen with the naked eye.

"It was a whopper," says Swift principal investigator Neil Gehrels of NASA's Goddard

Space Flight Center. "This blows away every gamma ray burst we've seen so far."

Swift's Burst Alert Telescope picked up the burst at 2:12 a.m. EDT on March 19, 2008, and pinpointed the coordinates in the constellation Bootes. Telescopes in space and on the ground quickly moved to observe the afterglow. The burst was named GRB 080319B and registered between 5 and 6 on the visual magnitude scale used by astronomers. (A magnitude 6 star is the dimmest visible to the human eye; magnitude 5 is almost three

times brighter.)

Later that evening, the Very Large Telescope in Chile and the Hobby-Eberly Telescope in Texas measured the burst's redshift at 0.94. A redshift is a measure of the distance to an object. A redshift of 0.94 translates into a distance of 7.5 billion light years, meaning the explosion took place 7.5 billion years ago, a time when the universe was less than half its current age and Earth had yet to form. This is more than half-way across the visible

universe.

"No other known ob-ject or type of explo-sion could be seen by the naked eye at such an immense distance," says Swift science

Astronomical News

Naked-eye Gamma Ray Burst


MERCURY starts April low in the dawn sky. On April 1 it will be just over 3° below Venus and a little to its right. Mercury will be about 6.5° above the horizon 40 minutes

before sunrise. With a magnitude -0.6 is should be readily visible in binoculars.

Very early April will present a last opportunity to find Mercury in the morning sky. The planet will get steadily lower in the dawn sky as it approaches superior conjunction with the Sun on April 16. After that date Mercury will be in the evening sky. However, even

by the end of April it will set only 30 minutes after the Sun so will not be observable.

MARS sets about 12 pm NZDT on April 1 and just after 10 pm NZST at the end of April. Hence it will be best placed for viewing as soon as the sky darkens in the early evening when it will be to the north and at its highest. During April the planet's magni-

tude will fade from 0.8 to 1.2.

Mars is in Gemini all month, starting about 1° to the right of the 3rd magnitude star ε Gem. By the end of April, Mars will have moved a few degrees east to be a little over 5° above Pollux, β Gem, the brightest star in the constellation. They may look similar as

both Mars and Pollux will have a magnitude 1.2 and both have a slightly orange colour.

On the evening of April 12, the 45% lit Moon will be 2° from Mars as seen from New Zealand. An occultation of Mars by the Moon will occur, but only be visible from ex-

treme NE Canada, Greenland, Iceland and northern parts of Scandinavia.

JUPITER moves further up into the morning sky, indeed once the clocks are set back an hour to NZST on April 6, it will be rising before midnight. By April 30 Jupiter will rise close to 10 pm. Even so the best time for viewing Jupiter, when at it is at its highest will be at the beginning of morning twilight. The planet remains in Sagittarius some 10° from the "Teapot's Handle" during April. Late in April, on the 27th, the 59% Moon will be just under 4° from Jupiter as they rise, by dawn they will be 6.5° apart, by which time the

Moon will be just over half a degree from the small 8th magnitude globular cluster, M75.

SATURN remains in Leo during April, close to the constellation's brightest star, Regulus magnitude 1.4. By the end of April the two will be little more than 2° apart with Saturn to the right of Regulus. At magnitude 0.5 Saturn is almost a magnitude brighter than

Regulus.

By April 30, Saturn will be setting at about 1.30 am. It will be at its highest and best placed for viewing mid evening during April. Observers will find that Saturn's rings do not appear very wide open, resulting in the overall brightness of the planet being lower

than in recent years.

The closest approach of the moon to Saturn is on the evening of April 15. At 7 pm the 76% lit Moon will be 5.2° from the planet, a distance dropping to 3° before it sets after midnight. The Moon will be even closer to Regulus, closing to about 20' before they set in New Zealand. The Moon will occult Regulus, but the event is only visible from parts of Antarctica south of India and Australia. Otherwise the event is almost entirely over

sea, missing the extreme southwest of Australia by barely 60km.

AAS Journal 10 April 2008 April 2008 15 AAS Journal

new Moon), quadratures (first and last quarter), perigees and apogees. This is a high rainfall location (average 2100 millimetres annually) with a high number of rain days (annual average 155 days of rain over 2 millimetres). Therefore, to minimise the effects of chance, I examined only heavy rain events, which I defined as more than 20 millime-tres over a period of one to four consecutive days. I deemed the rain event to be associ-ated with a Moon event if any part of it was within two days of the Moon event. Several cases were ambiguous with these protocols – in these cases I gave the benefit of the

doubt to the advantage of the forecasting method’s success.

Over the 50 calendar months there were 134 such rain events of which 112 were associ-ated with one or other of the six Moon events that occur each month. The other 22 rain events were unambiguously midway between Moon events. A ratio of 112 rain events out of 134 is 84 per cent. This sounds impressive, but there is a trap here. This is the proportion of heavy rain events associated with Moon events. It does not tell us how many Moon events were not associated with such rain events, so it does not indicate the rain-forecasting power of the Moon events. This is because the short time interval be-tween the monthly Moon events (maximum eight days and as little as two or three days when apogee or perigee fall midway between a syzygy and a quadrature), along with the tallying protocol used, dictate that nearly all rain events will be associated with a Moon

event.

The more valid indicator of the rain forecasting power of the Moon events is the propor-tion of Moon events associated with rain events. Over the 50 calendar months of my rain data there were 314 Moon events of which 112 were associated with heavy rain events

(35.67 per cent). The breakdown was as follows:

Of 52 full Moons 19 were associated with heavy rain events (36%)

Of 51 new Moons 19 were associated with heavy rain events (37%)

Of 51 first quarters 26 were associated with heavy rain events (51%)

Of 52 last quarters 14 were associated with heavy rain events (27%)

Of 54 perigees 21 were associated with heavy rain events (39%)

Of 54 apogees 13 were associated with heavy rain events (24%)

Obviously, if I had used any or all Moon events to forecast heavy rain at this location over this four-year period most of my forecasts would have been wrong. In spite of my generous data analysis protocols, these data demonstrate that the association between monthly Moon events and heavy rain events is no more than would be expected by chance. The associations are certainly not strong enough to indicate a causal link. Therefore, monthly Moon orbital positions would not have been useful predictors of such

rain events at this location over this period.

Ken Ring believes that perigee-syzygy alignments are good storm predictors. Two of these alignments are possible per year. Over the four years of my data there were seven of these alignments of which six were associated with heavy rain (85 per cent). This impressive result suggests that Ken Ring is right. However, in view of the other findings detailed above, it is probably a statistical hump that would smooth out with a larger sam-

ple of perigee-syzygy alignments.


would cause predictable weather events. You would also believe that the lesser tidal forces at the non-aligned times would cause predictable weather events. But what addi-tional effect could the node alignments have on tidal forces? The answer is almost none. When the Moon is on or near one of its nodes at full or new Moon it is only very slightly better aligned with the Sun and Earth than when it is not near one of its nodes at full or new Moon. The Moon is never separated more than five degrees from the plane of Earth’s orbit round the Sun. Such a small angular difference would make no significant difference to the tidal forces at Sun-Moon-Earth alignments. In any case, the tidal forces of the Moon on Earth’s atmosphere are about 300 times too weak to influence the weather. They are swamped by the vastly more energetic thermodynamic forces in the atmosphere that generate the weather, driven by the Sun’s heat (see my earlier articles in

this Journal, October and November 2004).

TABLE 1

Orbital periods of the Moon

Synodic Period: 29.531 days

Sidereal period: 27.322 days

Anomalistic period: 27.555 days

Nodical (draconic) period: 27.212 days

Long-term periods of the Moon

Saros Period (eclipse cycle): 6585.32 days

Revolution period of the nodes: 6797.16 days

Revolution period of the perigee: 3232.39 days

Ring’s current favourite period constant: 6231.03 days

Other terms used in this study

Length of the tropical year (the year of the seasons): 365.24219 days

As Erick Brenstrum discovered, Ken Ring decides arbitrarily to use any of several lunar periods for his long-term weather forecasts. Since Brenstrum’s investigations have shown that they don’t work very well for this purpose it won’t matter which he uses. As Brenstrum wrote, “If long-range forecasting were as easy as following the same sequence of weather as occurred 18 years and 10 days ago, the veracity of the method would have

been clearly established a long time ago and everyone would be using it.”

Apparently Ken Ring has backed the wrong horse in using multiples of the Moon’s syn-odic period for long-term weather forecasting. For short-term forecasts he believes the Moon’s syzygies and perigees are useful predictors of bad weather because the atmos-pheric tides are higher at these times than at quadratures and apogees (The Lunar Code pages 33, 82 and 84). Recently I investigated the success of this method for forecasting

heavy rain events month by month.

I have kept rain records at my home in South Hokianga since January 2004 and now have 50 calendar months of data to which I have added the Moon’s monthly syzygies (full and


Kenric Ma, 2008 Winner of the Harry

Williams Trophy

Prasad De Zoysa, 2008 Winner of

the Solar System section

John Wattie, 2008 Winner of the Artis-

tic section and his winning image

Partial solar eclipse (Feb 7, 2008)

through cloud

Some of our winning astrophotographers at the 2008 Burbidge Dinner

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I n my earlier article in this Journal (December 2005) I discussed meteorologist Erick Brenstrum’s discovery that Ken Ring uses the Saros cycle (18 years 10 days) for long-term daily weather forecasting by using a continuous sequence of old MetSer-

vice weather maps that are 18 years 10 days earlier than the day to which he applies it for

his long-term forecast.

Subsequently Brenstrum wrote an article in New Zealand Geographic (Number 79, May-June 2006) analysing Ring’s forecasting success with this method. He pointed out that New Zealand’s westerly flow patterns of normal weather make it quite easy to achieve an 80 per cent forecasting success by chance. For example, Blenheim averages 78 rain days per year, so if you forecast dry weather every day for a year in Blenheim your success rate would be about 80 per cent. Given this, Brenstrum deemed it more indicative to test success with the less common severe weather events, the most common being a strong

north-west flow ahead of an active front.

He found there were 22 such events in 2005, none of which were matched by a similar event on weather maps from 18 years and 10 days before. On the 1987 weather maps there were 17 such events, none of which were repeated 18 years and 10 days later. He found that Ring’s success rate for predicting heavy rain at Hokitika was 34 per cent even when allowing the most generous error window of two days either way. For Napier,

Blenheim and Christchurch his success rate was less than 20 per cent.

More recently Erick Brenstrum discovered that Ken Ring had stopped using the Saros period and, for daily forecasts in his Predict Weather Almanac for 2008, he used weather maps from 17 years 21 days earlier. Brenstrum reported this quantum leap in Ring’s method to me asking what this period had to do with the Moon’s orbit. Since Ring does-n’t divulge his secret number codes I had to figure it out. I marshalled the main lunar

orbital periods (Table 1) and did some number crunching.

The first thing I noticed was that Ring’s new period (6231.03 days) is almost exactly 12 lunar synodic periods less than the Saros period. This turned out to be the clue I needed. I also noticed that it is almost exactly 211 synodic periods and 229 nodical periods – that is, it is very close to a whole number of synodic and nodical periods. The nodical period

is actually something of a red herring, as I explain below.

After some calculations with the Moon’s anomalistic and sidereal periods I was able to eliminate them from the enquiry. The anomalistic period is the time interval between two successive passages of the Moon through its perigee (27.555 days). The perigee

Weather Forecasting By The Moon: An Update

Bill Keir


point moves around the star background in 8.85 years in the opposite direction to the mo-tion of the nodes (the perigee goes eastward, the nodes westward). I can be excused for thinking Ken Ring might have been using some long-term application of the anomalistic period because he has often claimed that perigee “spells trouble” with the weather. How-ever, I found no numerical coincidences that indicated his latest periodic constant is re-lated to the Moon’s anomalistic period. Similarly I found no such coincidences indicat-ing that he was using the sidereal period (the Moon’s orbital period in relation to the star

background, 27.322days).

The nodical period (also called the draconic period) is the time interval between two suc-cessive passages of the Moon through its ascending node (27.212 days). Since there are two nodes the Moon passes through each successively about every 14 days. The nodes revolve around the ecliptic against the star background in 18.61 years. [The nodes are the two points where the Moon’s orbit round Earth crosses the plane of Earth’s orbit around

the Sun.]

The Magic Synodic Period

I have concluded from my calculations that the Moon’s synodic period is Ken Ring’s favourite number code for his long-term weather forecasts. He mentions this preference in his latest book (The Lunar Code, 2006, page 97) but doesn’t explain beyond saying,

“the solar calendar was not set up with forecasting in mind”.

The synodic period is the time interval between two successive new Moons (29.531 days). This is the lunar month of ancient lunar calendars. If you believe that the geome-try of the Sun-Moon-Earth system influences Earth’s weather sufficiently to have weather forecasting power the synodic period will be your preferred tool because the changing geometry of the Sun-Moon-Earth repeats over any whole number of synodic periods. A characteristic of this period is that any pair of days a whole number of syn-odic periods apart will have almost identical Sun-Moon-Earth geometry. If you believed (or better still had evidence) that this had weather predicting power you could use any whole number of synodic periods to predict daily weather over any period. For example, any pair of days one synodic period apart will have almost identical Sun-Moon-Earth

geometry, as will any pair of days 200 synodic periods apart.

Assuming this is currently the basis of Ken Ring’s long-term weather forecasting I had to wonder why he has such a fixation on using the particular periods Erick Brenstrum dis-covered (6585.31 days, and 6231.03 days). It could only be because the nodical period comes into play over these intervals. The Moon’s nodes come into alignment with the full and new Moon about every six synodic periods (this makes eclipses possible at these times). So any multiple of these intervals of six synodic periods will also include a rough alignment of the nodes with the Sun-Moon-Earth alignments at full and new Moon. This means that the geometry of the Sun-Moon-Earth-Nodes will repeat almost exactly on any

pair of days six synodic periods apart, or any multiple thereof.

If you believe, as Ken Ring does, that tidal forces of the Moon on Earth’s atmosphere influence the weather sufficiently to have weather forecasting power, you would believe that the compounded tidal forces at Sun-Moon-Earth alignments (i.e. full and new Moon)

author of uranometria (5) introduction to astrophotography · 2012-05-30 · sk what's the...

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