the sky-watcher quattro 12-inch imaging...

Astronomy TECHNOLOGY TODAY 29

When I first started work-ing at Software Bisque, I neveradmitted to anyone that Imade any efforts at astropho-tography. My earliest attemptswere black-and-white film onthe Moon, and some stabs atthe planets with a homemadeweb cam-based video imager.Eventually, I acquired a DSLRand started shooting deep-skyobjects. As I progressed, I wentthrough a whole graveyard ofpoor-quality telescopes on myjourney to imaging nirvana.One of my worst nightmareswas my first “Imaging New-tonian.”

It was an 8-inch f/4 scopeI picked up at NEAF one yearand shipped home to myselfafter the show was over. I got itfor a song, and as they say, youget what you pay for. I endedup paying more for the TeleView Paracorr than I did forthe scope to correct for thecoma (not the fault of the

scope, this is inherent in allNewtonians), and I somewhatpainfully began what is now afull-blown obsession withdeep-sky imaging.

My problems with thatscope in particular started witha very loose mirror cell thatmoved, and would not holdcollimation. The same couldbe said for the spider vaneholding the secondary. It had alot of what at Software Bisquewe like to refer to as hysteresis,a bit of unpredictable flop in amechanical system. Collima-tion was like trying to wrestlea big slippery wet fish to theground.

The focuser was clearlynever intended for anythingother than an eyepiece, andevery time I’d slew to a newtarget, I’d have to refocus dueto the shift or flop (there’s thathysteresis again). Typically,“most” of the frame would bein good focus. Still, I managed

By Richard W. Wright, Jr.

The Sky-Watcher Quattro 12-inch Imaging Newt

A Quest for Glorious Diffraction Spikes

Image 1 - Quattro 12-inch ready for action.

some images with my unmodified CanonT1i, and the imaging fire was fueled, soin a sense, it served its purpose. I finally

gave it away at my astronomy club’s starparty to someone more mechanically in-clined than I, and he fixed it up and was

eventually quite happy with it.Over time, I grew better at what I

was doing, and of course acquired better

30 Astronomy TECHNOLOGY TODAY

THE SKY-WATCHER QUATTRO 12-INCH IMAGING NEWT

Image 2 - Yes, it’s as big as my couch. Image 3 - Mirror cell out of the box.

equipment, primarily fueled initially bymy growing involvement in the imagingside of things where I worked. I havesome nice instruments today, someworld-class refractors, exotic catadioptricdesigns, etc. I gave away my laser colli-mators and smugly declared I’d never go

back to slumming it with an imagingNewtonian. I was of course, quite wrong.

There is simply no denying that awell-made, well-corrected Newtonian as-trograph is one of the best values (bangfor the buck) on the market today. Theyare inexpensive to make, and simple. You

just need to avoid one that is too cheaplymade.

A friend of mine makes custom New-tonian astrographs, and the quality of hiswork, and the resulting images, began tosway my conception of these as “lowclass” instruments. Here is a way to get



Image 4 - Don’t over tighten! Image 5 - Mirror cell from the back.



really large apertures, without a secondmortgage. So it was again one year ago atNEAF that I came by the Sky-Watcherbooth to chat it up with my friend KevinLeGore. They had a new imaging New-tonian on display there, and I recountedmy story of woe when I first got startedimaging.

Somehow, we got to talking abouthow I missed diffraction spikes, becausethey really punch up objects like openclusters, and what a great value a New-tonian really was. I wished him luck withthe new product. He called me a fewmonths later and asked if I’d like to tryout one of the 12-inch models, because Iwas one of the few people he knew witha mount that could handle it. I immedi-ately thought how nice the Pleiadeswould look with great big diffractionspikes, and so of course I said yes. A fewweeks later, a box the size of a hot waterheater showed up on my front porch.

Some Assembly RequiredThe Quattro 12-inch actually came

in two boxes. One contained the mainbody of the tube and all the accessories,and another well-packed box containedthe 12-inch mirror. I thought this wasmuch smarter than trying to ship a largerectangular box that was especially heavyon one end; that would be a recipe fortrouble during shipment.

The mirror cell is simple to put to-gether, and the collimation push/pull sys-tem is tight and slop free. Speaking oftight, one thing to be careful of is yourown sense that everything must be tightdown here. The mirror itself is already inthe cell, held in place by three rubber-re-taining clamps. These felt loose to me, soI immediately tightened them downwithout thinking. A subsequent call toKevin at Sky-Watcher informed me thatthis stresses the mirror and will deform itever so slightly, causing image distortion.

Image 6 - Protruding bolts prevented sliding into the versa-plate.

Image 7 - A retrofit to the dovetail as needed for my mount’s Losmandy D-style connection.



Unless the mirror is literally slidingaround, don’t over do it here!

I’ve always felt an attraction towardssmall, compact scopes, and this 12-inchis now the largest instrument I have useof. I have to say, though, 12 inches ofmirror is a glorious sight to behold.

What you’re really assembling is themirror cell with the bracket that goes onthe back of the scope. Once assembled,you just set the scope on the ground bot-tom up, turn the mirror cell over anddrop it right on. A set of Philips-headscrews around the periphery will hold itin place.

This is a big piece of Borosilicateglass, and the rear cell comes predrilledfor attaching a fan if needed. The opendesign of a Newtonian also helps a lotwith cooling, but the black paint doesmake for a hot scope in the Florida sun.I keep the scope covered with a reflective

Image 8 - Ready to go with a DSLR.

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cover during the day and only uncover itafter the sun has set. I’ve found so far thatby astronomical twilight, the scope isready to go, but the very best images withambient cooling are still a good hour

away without a fan to help the mirrorcool off. I also live in a climate where thetemperature does not drop that much atnight. As they say these days, yourmileage may vary. Sky-Watcher USA

does not offer a specific fan kit for thisscope, but adapting a fan to the rear cellshould not require a feat of mechanicalengineering.

My first and only mechanical chal-lenge with this scope was the includedLosmandy-D dovetail. I have three Para-mounts and at pounds assembled, thiswill need to go on my MX+ or ME II.

The issue is that the dovetail was at-tached in such a way as to easily facilitatemounts where the scope “rocks” in fromthe side, and then clamps down on thedovetail. On the Paramount’s versa plate,we do this for the really big scopes withan additional bracket adapter, but inParamount Land, a 12-inch scope is notreally very big. The versa plate is designedso that smaller scopes slide in from thetop or bottom, and the large bolts on ei-ther side of the dovetail prevented this.The dovetail is also shorter than the versaplate, so the option to unbolt one side



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Image 9 - Don’t expect this to work well on a scope this size



during mounting would not work either.At first, I found a spare dovetail in

my shed, but it required mounting hescope off balance to one side. I tried thisin the backyard, and it seemed stable, butI opted instead to get a new universaldovetail directly from Losmandy. Thishas a nice recessed hole in the center thatallowed the scope to slide easily in placeon the Paramount’s versa-plate.

So let me think … what did I dowith that HoTech laser collimator Ibought a few years back? Oh yes, I tradedit at a swap meet for a set of rings! One ofthe lessons learned in my earlier New-tonian years was that cheap laser collima-tors were good for one thing; teasing yourneighbor’s cat. A quick visit to the OPTwebsite, and I was back in the Newtonian

collimation business a few days later witha brand new HoTech laser. This time I’llhang on to it!

Unlike my earlier experiences, thiswas a breeze. A tweak to one screw on thesecondary brought the laser to the centerof the primary mirror, and a few adjust-ments to the main mirror cell centeredthe reflected laser back on the collimatorstarget. Piece of cake. No Newtonian isgoing to arrive after shipment collimated,much less if you have to put the mirrorcell on yourself. I was actually starting tofeel the excitement of getting this beastout under the stars.

First LightI took the Quattro down to my ob-

servatory under darker skies than where

I live in Central Florida. Also includedfor evaluation was the optional $285coma corrector. The back focus for thiswas 55 mm, and the same Canon DSLRadapter I use on my two Sky-Watcher Es-prits fit it perfectly and placed the chipthe correct distance from the backthreads. For my first attempt, I decidedto go full frame and put on my Canon5D Mark III, which is unmodified, andused a Lodestar-powered guide scope Iplaced in the finder-scope bracket.

My resulting configuration was 1220mm of focal length (the coma correctordoes not modify the focal length, by theway), at f/4 on a full-frame DSLR chip.This would be a good test of how widethe corrected field was, and a DSLRshould do very well at f/4. One of the ad-

Image 10 - Glorious diffraction spikes!



vantages of a large chip, too, is that evenat 1220 mm of focal length, I could fitthe entire Pleiades star cluster in the fieldof view! Being that the camera was un-modified, a reflection nebula would suitit just fine, and I was hoping for someglorious diffraction spikes as a reward formy return to the Newtonian camp. I wasnot disappointed.

First though, I have to point out thatguiding in this configuration did notwork out that well. A secondary guidescope such as this works well for me onthe Esprit 150, but the Esprit is operatingat a slightly shorter focal length (1050

mm), and is more rigid. This large scopewith a metal body flexes considerably,and the old guiding nemesis – differen-tial flexure – reared its ugly head afteronly about three minutes of exposuretime.

Differential flexure is when the opti-cal axis of the main imager and the guidecamera start to drift apart over time dueto the ways the two different mechanicalsystems are flexing over time. A thou-sandth of an inch difference can work outto many arc seconds of error in yourguider images. On subsequent nights, Iwould successfully go with an off axis

guider on a CCD, or use the Paramount’sProTrack features to defeat this. Thesmaller Quattros, likely as well, would beless sensitive to this.

The focuser does its job and whilecertainly not a premium model, it holdsa DSLR or small CCD camera well,doesn’t slip, and doesn’t rock back andforth. A 10-to-1 ratio Crawford-style re-duction knob makes focusing by handpossible. The one issue with not havingautomated focusing is, of course, this is aBIG scope, and access to the focuserknobs while pointed to a high object maybe awkward or not even possible. This

Image 11 - Corner performance was reasonable.

was compounded by my habit of placingthe focuser UP instead of off to the sidein order to maintain better balance andless flexing on the imaging train. Fortu-nately, I was able to focus on a lower starin the sky, and the focuser would holdfocus when I slewed to a higher target.Focus will of course shift over the night asthe metal tube retracts while it cools off.I did not find this to be a problem, how-ever, as you have to give the instrument

an hour or so anyway for the mirror tocool and get best results.

Back to Evening #1I ended up with a pile of short expo-

sures on the Pleiades at ISO 800. Whilenot as deep as I’ve gone on this subject be-fore, I must say the diffraction spikes onthe stars are glorious, and make up for thelack of depth. This object was my youngestson’s favorite, and he preferred the less deep

treatments of some of my earlier images ofM45. He had passed away recently, andthis was my first attempt back under thestars since then, and so I shot these partiallyin his honor as well. I think he would havebeen very pleased.

It’s also worth noting perhaps that, thisparticular evening, my wife had comealong for the first time ever to get awayfrom the house (and I didn’t want to leaveher alone … or be alone myself at that



Image 12 - Messier 46 and two companion planetary nebula.



time). I was simply not in the mood forfighting with imaging equipment, and Ihad already resigned myself that this mightbe “just a camping trip,” and I didn’t careif I got any images or not.

I mention this mostly to highlightwhat a hassle free experience this was forme that night. Short of a refractor, an im-aging Newtonian, however, is a very simpleimaging system, and my first night outwith the Quattro, everything “justworked,” and other than the short expo-sures was stress free. This was wonderfuland timely at a time when my imagingacumen was not really up to its normal

standards.Corner performance was not up to the

standards of the Sky-Watcher Esprit 150on this large a chip, but it was still prettygood. Zoomed in, the stars are clearlyshowing some distortion, but a slightly re-sampled (shrunk) image is still very goodto the eye on a computer screen. On any-thing other than a full-frame chip, I ex-pected the field to be nearly perfect in thecorners, and I did find this to be the case.

Practice Makes PerfectFor subsequent adventures with the

Quattro, I again choose to shoot with my

unmodified Canon 5D, as it provided anice large field of view at the longer focallength of the Quattro 12-inch, and I wouldshoot some clusters where a modifiedDSLR was not needed. I found that Icould go a bit longer unguided than guidedbecause of the flexure, and four or fiveminutes was all I needed to shoot someopen clusters with a DSLR at f/4.

Now, my very considered personalopinion is that open clusters are beautifulin an eyepiece, but just plain boring oncamera. Without the dynamic range of atrue visual view, the camera just cannot dothem justice. But … imaged through a

Image 13 - A sparkling Globular Cluster.

Newtonian, you get very nice diffractionspikes on the stars, and it does just makethem seem to sparkle! I shot both M37 andM46, and just the hint of diffraction spikesreally adds to the image.

Messier 46 in particular is a real gemin the eyepiece, and it turned out ratherwell, I think, on camera too with the Quat-tro. A cropped down version shows thatnot only did the planetary nebula NGC2438 show up prominently, but I also cap-tured the smaller lesser-known companionplanetary nebula PK231+4.1.

I also made some shots with theStarlight Xpress Trius 694, using an off-axisguider. At f/4, I only needed five-minuteexposures to go deep enough on anythingI wanted. The Sony 694 is a much smallerchip than the full-frame Canon, and thestars were well corrected over the entirefield. With smaller pixels and the long focallength, I went after a different set of targets(and needed to be able to guide withouthaving to do an extensive mount model).

First, I shot the globular cluster M53.Globular clusters are my favorite object in

the eyepiece, and sometimes come closephotographically. I was very happy withM53, with the smaller central stars show-ing a powdery quality, and the brighter sur-rounding stars having that “sparkle” thatonly a Newtonian can deliver (and don’tget me started on adding diffraction spikeswith Photoshop!).

I also shot Messier 81, as the galaxyfilled the field of view splendidly on theSony chip. Again, that sparkle around thegalaxy just really adds to the image.

Finally, I had to try out the scope on



Image 14 - M81 fills the frame.

the ever-popular M42. I experimented tosee how long I could go and still pull thetrapezium out before over exposing; twominutes. Again, I find the subtle “sparkle”of the surrounding stars adds just a bit ofcharacter to the image that my other im-ages of this object lack.

ConclusionI have no hesitation in recommending

the Quattro as a great starter imaging scopecapable of delivering images any experi-

enced imager will also be happy with. I’dprobably recommend for the beginner oneof the smaller models, as a shorter focallength is easier to deal with when gettingstarted. Also, you’ll need a very well mademount to put the 12-inch model on. As forme, I’m not done with this scope. I usedto have a nearly post-traumatic stress re-sponse to the idea of collimating a New-tonian scope, and I can say I’m cured nowthat I have an instrument that didn’t cuttoo many corners to keep it “cheap.”

There are a lot of nice perks to a 12-inch mirror, and for sure I’m going toremove the coma corrector and try itsoon on the Moon and planets with aBarlow and a high-speed CMOS imager.F/4 is also a nice photographic speed for shooting emission objects, and the focal length means I can get in tighton some interesting targets, perhaps evenshooting some narrowband. All I need now are some clear skies and good weather!



Image 15 - Jewel of the Winter Sky fills a CCD frame.

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