astronomy...astronomy technologytoday yourcompleteguidetoastronomicalequipment volume8•issue1...

ASTRONOMYTECHNOLOGY TODAYYour Complete Guide to Astronomical Equipment

Volume 8 • Issue 1January-February 2014 $6.00 US

SKY-WATCHER USA PROED 80-MM AND 100-MM APO REFRACTORS • HUBBLE OPTICS UL18 F/4.5

BAADER PLANETARIUM COOL-CERAMIC SAFETY HERSCHEL WEDGE • CANON’S VARI-ANGLE LCD MONITOR

ASTRONOMIK CLIP-FILTER SYSTEM • DARK SKIES APPAREL OBSERVING VESTS AND HOODS

HubbleOpticsUL18 f/4.5

THE UNIVERSE IS YOUR STUDIO. CREATE YOUR MASTERPIECE.

Create stunning lunar, solar, and planetary images with Celestron’s new USB 3.0 CCD

camera: SKYRIS™. We’ve joined forces with The Imaging Source® to design this cutting-edge

camera from the ground up. SKYRIS features fast frame rates and shutter speeds, allowing

you to capture planets during brief moments of stable air. Then, using the included iCap and

stacking software, you can stack your best images to create vibrant color or monochrome

images of Saturn, solar prominences, lunar craters, and so much more. It’s available with a

variety of popular Sony imaging sensors, so there’s a SKYRIS to meet any imager’s needs.

CELESTRON PREMIER SELECT DEALERS

// Six models for planteary, lunar, and solar imaging

// Highly-sensitive Exview HAD Sony Color and Monochrome CCDs

// High-speed USB 3.0 connection enables fastest frame rate possible

// 12-bit output provides higher dynamic range

// Heat sink housing minimizes CCD noise

// Includes metal 1.25” nosepiece, 10’ USB 3.0 cable, Celestron iCap software, and stacking software.

Adorama – 800.223.2500 – www.adorama.com Astronomics – 800.422.7876 – www.astronomics.comB&H Photo – 800.947.9970 – www.bhphotovideo.comFocus Camera – 800.221.0828 – www.focuscamera.comHands On Optics – 866.726.7371 – www.handsonoptics.com

High Point Scientific – 800.266.9590 – www.highpointscientific.comOPT Telescopes – 800.483.6287 – www.opttelescopes.comOptics Planet – 800.504.5897 – www.opticsplanet.comTelescopes.com – 888.988.9876 – www.telescopes.com Woodland Hills – 888.427.8766 – www.telescopes.net

Moon, SKYRIS 274C

Planets, SKYRIS 618M

Today’s Dobsonian telescopes, orDobs, have gone through many evolu-tionary phases over the past 50 years. Noother telescope design has seen so many it-erations. Dobsonians now come in an im-pressive range of shapes and sizes and aremade from a variety of materials and parts,but the essential design of John Dobson’soriginal concept still holds up well. Manyamateur telescope makers (ATM) havetaken advantage of how simple Dobs areto build and have greatly improved onearly designs. You can go to any star partyand see numerous variations, each with itspros and cons.

Many commercial Dobsonians are de-rived from basic ATM designs. Dobs areoften described as light buckets, and thispretty much sums up the appearance ofmany of them – big, bulky and heavy. Thelatest commercial trend is toward ultra-lights or ultra-compacts, reversing the no-tion that big aperture means a gigantic,bulky telescope.

Several manufacturers now have ul-tralights in their catalogs, including suc-cessful offerings from Obsession. Thenthere is the Hong Kong-based company,Hubble Optics. The name alone gives itsome immediate name recognition. Hub-ble Optics has been in business for about10 years and is run by Tong Liu.

One thing I have realized in my fairlyshort time with this hobby is that we al-

ways want more and more aperture. Buton the flip side, more aperture also meansbigger and heavier telescopes as we getolder. At a certain point you start to limityourself, because lifting and moving such

big telescopes gets harder with age. Thiswas the case with my previous telescope, a16-inchMeade LightBridge. Optically, thetelescope itself is fine, but its weight dis-couraged frequent use or carrying it to

Astronomy TECHNOLOGY TODAY 35

Image 1 - The UL18 shown fully assembled with the author’s homemade mirror cover inplace.

By Andy Cheng

Hubble OpticsHubble UL18 f/4.5An Ultra-Portable, Ultra-Affordable Big Dob

36 Astronomy TECHNOLOGY TODAY

public events. It weighed more than 128pounds, according to Meade’s specs, witheverything assembled.

With any new telescope purchase, Ido a lot research before forking out the bigbucks. I found comments on the webabout a Hubble Optics 14-inch ultralight(UL) and had heard of the companythanks to some magazine ads, but didn’tfind much more online. I emailed HubbleOptics president Tong Liu, who answeredall of my questions and addressed my con-cerns.

I decided to purchase the HubbleUL18, figuring I might as well upgradefrom 16 inches of aperture to 18. My eyesaren’t getting any better, and I need all theaperture I can afford. My back was also en-joying the idea of moving an 72-pound-plus telescope (per Hubble Optics’ specs)

versus 128-pounds-plus.The Hubble UL18 was very compet-

itively priced at about 30 percent less thanits main competition. Some alternativesoffer more standard accessories, but theiroverall designs and specs are similar, minusthe actual mirror design, which I will getinto later.

Tong has been making commercialmirrors for a while and has been activelyinvolved with the Alt-Az Telescope Initia-tive organized by Russ Genet. The basicdesign of the Hubble Optics UL Dobscame from this cooperative collaboration.

After about 50-plus emails, I orderedthe telescope. Tong said it usually tookabout 60 days for the order to be com-pleted. Unfortunately, that doesn’t includeshipping time. Fast-forward a few months,when I received the 18-inch sandwich mir-

ror separately and the structure about amonth after that. I would have gotteneverything about three weeks sooner if Ihadn’t run into some U.S. Customs issuesas a consequence of using the U.S. PostalService for international shipping.

It’s all about the GlassOne of the major points that drew me

to Hubble Optics telescopes, besides theultralight design, was its sandwich mirrors.There are only a few companies through-out the world that make lightweight mir-ror cores. Hubble Optics’ design allows thefabrication of large-aperture mirrors thatnot only weigh less than solid-core blanks,but also cool faster – much faster.

A sandwich mirror is just what itsounds like: two sheets of glass joined to-gether. The front sheet is ground and pol-ished to specific measurements. The rearsheet is of the same diameter and similarthickness, and is separated from the frontsheet by a layer of short glass rods or pegs.Viewed from certain directions, the mir-ror has an almost honeycomb look.Viewed from the back, the rod ends looklike dimples on a golf ball.

The design achieves a roughly 20-per-cent reduction in weight and creates moreglass-to-air surface area for better cooling.According to Hubble Optics, the mirrordesign cools so well, it doesn’t even offercooling fans as an option.

Some Assembly RequiredAnother benefit to this telescope de-

BUY A FRIENDA GIFT

SUBSCRIPTION!

SUBSCRIBE NOW!!!

ASTRONOMYTECHNOLOGY TODAYwww.astronomytechnologytoday.com

Image 2 - Cross-section view of the sandwich primary.

HUBBLE OPTICS HUBBLE UL18 F/4.5

sign, besides its lighter weight, is that it canbe disassembled into some surprisinglysmall pieces. You can easily pack it into ahatchback car with room to spare.

But a better description of the Hub-ble Optics ultralight might be “kit tele-scope.” The phrase “some assemblyrequired” is not lost on this design. Almostall telescopes require some assembly, butthere are certainly degrees, and it is amaz-ing how many nuts and bolts come withthe Hubble UL. And be prepared for met-ric if you are living in the U.S. Fortunately,the Hubble UL uses just two bolt sizes: 5-and 6-mm.

All of the eight truss tube bolts haverosette-type knobs for tool-free assemblyand are easy to identify. I wish HubbleOptics had used more tool-free bolts forother parts of the structure – one of myfirst modifications was to purchase wing-headed bolts to replace as many hex boltsas I could.

I found the assembly manual less thanadequate. Hubble Optics sent updatedmanuals, but I wish they were written byIkea for more clarity and greater detail.While the telescope used only two diame-ters of metric bolts, each came in multi-tude of lengths with no clear indication ofwhich length bolt went where. I invested alot of trial and error into finding the opti-mummatches of bolt lengths to bolt holes.

The turntable and mirror-cell boxwere shipped pretty much assembled. Themirror cell just needed the traditional 27-point mirror-cell points installed alongwith the wire rods between them. I think

the design would have been better if thecell’s wire rods were pre-bent for more con-sistent installation. This doesn’t affect theperformance of the mirror cell; it wouldjust look better.

I purchased the optional SkyHubWireless & USB Digital Setting Circle(DSC) System to help me better navigatewith the telescope. The hardware was de-signed specifically for the UL18, but aftersome head scratching, I realized there wasa screw hole missing, meaning I couldn’tinstall the DSC completely. I emailedTong, attaching photos of the telescope,and he confirmed they had missed drillingand tapping a hole for one of the encoderarms.With some trepidation, I went aheadand drilled and tapped the hole myself.


Image 3 - The UL18 disassembled and ready for transport.


The DSC system now works fine, but thatscrew hole interferes with installation ofthe optional wheelbarrow handles I hadordered. I now have to unscrew this DSCbolt to attach the handles, and worry Imay lose it someday.

As for the wheelbarrow handles, thefirst set was fabricated from thin, corru-gated aluminum, and they bent after oneuse. Hubble Optics sent a pair of new-and-improved steel handles which solved theproblem.

The mirror cell came mostly assem-bled, only requiring installation of supportplates – but installing the 18-inch mirrorwas something else. This took me a fewtries before I mastered fitting and tighten-ing the mirror properly into the sling. Themirror sling would benefit from finding aneasier way to make field adjustments whenthe mirror is loosened during transport.

A mirror cover was not available whenI ordered my UL18, but Hubble Optics


Image 4 - The UL18 fits easily in the back of an SUV.

Sizes for SBIG, QSI, FLI

Durable to extreme weather �uctuations

Non-re�ective

20+ years of thin �lm design

Manufactured in Vermont


now offers this accessory. The design of thetelescope makes it pretty easy to fabricateyour own, so I did. There is a nice metalframe around and above the mirror, so youjust need a rectangular piece of ABS plas-tic and some sticky Velcro to secure it. Ialso use an Astrozap bonnet cover to pro-tect the mirror.

As for the rest of the assembly, the sec-ondary cage includes a lot of parts. Boltholes are provided for mounting the two-speed Crawford focuser in one of severalalternative positions. I found it best tomount the focuser upside-down for betteraccess to the focus wheels.

The 4-inch secondary mirror sitsabove the cage, exposed to both stray lightand dew. I fabricated a light shield, againfrom ABS plastic, and also attached it withVelcro. I added a Kendrick secondary dewheater before assembly.

The secondary cage is thick alu-minum and looks to be cast as a singlepiece, instead of welded. There is minorflex in the spider vanes holding the sec-ondary, but not enough to affect the func-tion of the scope.

The eight truss tubes are powdercoated and appear narrow when comparedto standard truss Dobs of this aperture. Icould detect only minuscule flexing, andthe scope settles within a second of slew-ing.

I purchased the optional shroud,

which consists of thick Lycra-type mate-rial. It can sag into the light path in stockconfiguration, so I added clips to tighten itpending a better solution.

First Light with“The Hatchet Scope”

I ordered this telescope in December,but didn’t get it fully assembled until lateApril, so first light was at the Texas Star

Party (TSP) in Fort Davis, Texas. Whenmy friends bemoaned the superstition thatbuying new optics would bring cloudyweather for a week, I allayed their fears bynoting that I had actually received thescope a month earlier. Fortunately, theweather gods listened and TSP wasn’t awashout.

Luckily, I had a chance to test colli-mation before traveling to TSP and found


Image 5 - View of the 18-point mirror cell. Note the brass collimation knobs and positionof the SkyHub DSC electronics.

w w w. o f f i c i n a s t e l l a r e . c o m

NEW VELOCE RH250: Riccardi-Honders astrograph, 250 mm (F/5.6), long back focus extraction 200 mm, RSM spot size under 3.6 micron on the full 60 mm �eld, di�ration limited in the 400-800 nm range, 95 mm clear aperture digital focuser. Come and see it at the Winter Star Party, Florida, starting from February 23rd.

OS Flagship Dealers in USA: www.bisque.com - www.nmsouthernskies.com - www.optcorp.com - www.telescopes.netGA

LLER

Y

FAST - WIDEFIELD - COMPACT

THAT’S VELOCE !

EASY TO USE, EASY TO ALIGN: AMAZING PERFORMANCE

YGA

LLER

. c o mee l l a r. o f f i c i n a s twww

.nmsouthewwom - w.c.bisquelagship D

wwwealers in USA:g

bOS F

wom - w.corpc.optwwom - w.ciesrnsk

VES’TTHAATWIDEFIELD-ASTTFFAST

.netopeselesc.tww

!OCEELTCAACOMPPACCOMP--DD



another issue: mirror springs. In my expe-rience, this is typical with most productionDobs – my LightBridge had a similarissue. The stock springs on the UL18 werepretty small given its aperture, so I re-placed them with stronger springs frommy local hardware store.

Collimation is adjusted with knurled-brass knobs. These are nice, but I wouldhave preferred larger rosette knobs. Thelocking screws are too close to the colli-mation knobs to use anything other thanhex bolts for that function.

Once set up under TSP’s extremelydark and dry skies, I got first light.With somany options, it was hard to pick what toview first. One of my first targets wasOmega Centauri, which rose around11:00 p.m. Among the claims for theHubble Optics UL design is that there isno need for balance weights. I am sorry tosay that is not the case when the scope isfitted with the heavy combination of aParacorr Type 2 and Nagler eyepiece. Adda 9x50 optical finder and Telrad, and

Image 6 - The UL18 secondary cage with 2-inch Crayford focuser and 8x50 finderscope at-tached.


things start to go south – literally.The telescope would not hold at a low

altitude while trying to view Omega Cen-tauri so close to the horizon, so I jury-rigged makeshift counterweights. I hadsome tripod heads and clamps, but whatreally helped was attaching a heavy redhatchet borrowed from my observingneighbor. So for the whole week at TSP,my new scope was nicknamed “TheHatchet Scope.” Many folks dropped byjust to see what that was about.

Once balance issues were worked out,the optical properties of the Hubble Op-tics proved first-rate. Collimation held welland star tests showed I had at least assem-bled it correctly enough to get some verygood views. The two-speed Crayford fo-cuser worked well, and the scope producednice pinpoint stars with perfect diffractionspikes. It provided excellent views of manygalaxies in the Virgo area. Compared tothe views I was accustomed to from 16inches of aperture, the larger, faster UL18brought out many more dust lanes andother details I had not seen before.

Omega Centauri, in all its glory, wastruly beautiful. Using a 13-mm Ethos, Icould tell a huge difference with this tele-scope. Other observers were also doingoohs and aahs when viewing through thescope. Planetary views were also very nice.Saturn was spot on, and I could see band-ing and breaks in the rings. Since this tel-escope is very fast, a Paracorr Type-2 isdefinitely a must-have accessory to correctcoma.

Star parties are always fun and in-formative.With so many telescope designsin one place, the chances of seeing dupli-cates of any telescope is always higher, andthis was the case for me, but in an odd sortof way. At TSP, you stay in bunkhouses,each housing about six people. Mine in-cluded an observer fromWyoming namedSteve. We chatted a bit, but it wasn’t untillater in the week that we discovered weeach had a new Hubble Optics telescope.Mine was the 18-inch and Steve’s was the16-inch.We were both pretty much doingfirst light on our respective Hubble ULs.

We compared some notes, and he was en-joying his new toy as well.

What I Would ChangeIf I had a magic wand and had a

chance to change a few things about thistelescope, here is the short list.

Because ultralights have foldingrocker arms for portability, there is a small

gap in the arm. When moving the tele-scope in altitude, you get a slight “bump”at that gap. This was annoying at first,but, since it really doesn’t impede thefunction of the scope, it is a minor quib-ble.

Another is the Teflon altitude-bearingpads. The bottom turntable base and therocker box are two separate pieces, and


Image 7 - The UL18 with red-hatchet counterweight attached. Hey, it worked!

Image 8 - Details of the UL18 turntable base with SkyHub DSC encoder arm installed.


the Teflon pads on the base are either toonarrow, or there needs to be a better wayto keep the alignment on the rocker boxwith regards to the base. The telescopesometimes veers a bit to the edges of theTeflon pads, requiring that I nudge it backinto place.

Inherent to the design of most ultra-light Dobs is a low base – so low, in fact,that anything less than a clear, flat surfacecan interfere with movement of the scopein azimuth. The addition of a stable, flatplatform is required when using the tele-

scope on grassy or uneven surfaces.Finally, the standard configuration

of the secondary cage allows it to ride upthe truss-tube bolts if they are nottightened well enough, which can affectcollimation.

Final ThoughtsDespite that, in hindsight, this review

reads more like a laundry list of short-comings than a positive recommendation,I am very pleased with the UL18. I’ve fo-cused on negatives for the sake of brutal

honesty and neglected much of what isgreat about the scope in the process. Thekey components, the optics, are excellent,and most of the negatives I’ve noted werecured with the described easy modifica-tions.

I was initially worried about makingsuch a large purchase from what to a U.S.buyer is an overseas company, but Hub-ble Optics has been very responsive inevery respect. While they can’t send thingsovernight without undue cost, standardshipping is only about two weeks. Hub-ble Optics offers a large selection of op-tional accessories, and I recommend themas they are custom matched for HubbleUL design.

Hubble Optics also has some excitingnew Hubble ULs in the pipeline. A new20-inch f/4.2 and an f/3.7 are currentlyavailable, and they plan on introducinga 24-inch f/3.6. If my experience withthe Hubble UL18 is any indication, eachof these new products should be a homerun.

Is an ultralight Dob in your future?As larger apertures become more com-mon, the prospect of not having to tow atrailer and dedicated equipment just totransport your telescope may sway you to-ward an ultralight. Not only will you seemore distant objects, but your back willthank you as well.



Image 9 - The UL18 set up and ready for first light at TSP.

SPECIFICATIONS:

Optical diameter: ................................................................................................................................457.2 mm.Focal length:........................................................................................................~1860 mm (f/4); ~2058 mm (f/4.5).Eyepiece height at zenith: .............................................................~1730 mm, 68 inches (f/4); ~1930 mm, 76 inches (f/4.5).Optics type: .............................................................................................................................Parabolic primary.Optical quality: ..............Diffraction limited++ (Strehl 0.95+ for the primary mirror, 1/10 lambda or better for the secondary mirror).Focuser: ..............................................................................................2-inch dual-speed Crayford with linear bearing.Secondary mirror obstruction:.....................................................................................................................90 mm.Secondary mirror obstruction by diameter:...............................................................19.7 percent (f/4), 17.2 percent (f/4.5).Secondary mirror obstruction by area: .......................................................................3.9 percent (f/4), 3.0 percent (f/4.5).Mirror coatings/over-coatings: ......92-percent semi-enhanced aluminum on the primary and 96-percent enhanced on the secondary.Tube material: ..........................................................6063-T6 aluminum-alloy tubes with black stainless-steel knob screws.Aluminum-alloy main structure (OTA and mount) and structural-steel mirror cell.Length of optical tube: ............................................................~72 inches, 1828.8 mm (f/4), ~79 inches, 2006.6 mm (f/4.5).Weight, optical tube:..........................................................................................................62 pounds, 28 kilograms.Weight, fully assembled:.....................................................................................................72 pounds, 32 kilograms.

astronomy...astronomy technologytoday yourcompleteguidetoastronomicalequipment volume8•issue1...

Documents