Sunday, May 13, 2012

 

Frankenscope!


I told y’all the story of my Ultima C8, Celeste, the other day, muchachos. The denouement was that I removed the C8 OTA from its beautiful fork and placed it on a CG5 German equatorial mount when I just couldn’t live without go-to no more. After a while, howsomeever, I became nostalgic for the old no-computer C8 setup. It seemed a shame to let to that big, beautiful fork rot away, so when an unlooked for C8 tube fell into my hands, I put it on the Ultima’s fork mount. Which is a story in itself…

It began one sunny afternoon (must have been). I had just put the finishing touches on the copy—the text—for my second SCT book. I was almost done with Choosing and Using a New CAT. All I needed was a few more pictures, terrestrial type pictures. I had sworn that, unlike my original CAT book, this one would not want for photos. One thing I wanted to illustrate was the removal of a Schmidt Cassegrain’s corrector plate.

It would not be a big deal to pull Celeste’s or my number two C8’s corrector, taking pictures as I went. But I wanted to go further. I wanted to show the removal of a C8’s primary mirror and other potentially dicey things. I wasn’t askeered, but doing that to either of my beloved C8s did make me just a mite nervous in the service. What if I glommed onto another C8?

It wouldn’t have to be pristine. It wouldn’t have to work right. It wouldn’t have to work at all. All it would need would be a corrector plate and a primary mirror for me to remove. I started searching the usual venues—Astromart and Cloudy Nights—for unloved C8 tubes. With little success. There were plenty of scopes of various ages and conditions for sale, but I did not run across one in poor enough shape that it would go for the 100 – 150 bucks or less I had in mind.

I didn’t give up hope. I put out the call on my SCT User Yahoogroup. This e-mailing list, which I started in 1999 (and whose beginnings might be the subject of a blog some Sunday), is inhabited by the most knowledgeable Schmidt Cassegrain enthusiasts in the world. If I’ve learned anything about my favorite variety of telescope beyond the bare essentials over the last thirteen years, they are responsible. They are also some of the nicest amateurs around, and since, as I always say, amateur astronomers are the nicest folks anywhere, that is something.

It wasn’t long before I had a reply. One thoughtful individual had a hangar queen of a C8 he wasn’t using, needed fixing, and that he wouldn’t use even if it was fixed. He was more than willing to volunteer this scope for the cause. Naturally I jumped at the offer, insisting (I had to insist) on paying the freight.

When the package arrived, I tore into it and had a look. What I had before me was a black tube Celestron 8 OTA whose serial number seemed to indicate it was manufactured in 1984. Maybe. Celestron serial numbers have always been purty wacky. Just when you think you have cracked their strange code (which changed a time or three), you find a telescope that doesn’t fit the pattern. Serial number aside, the “ribbed” rear cell indicated this wasn’t no spring chicken. Another tip-off to the C8’s vintage was the weird stuff on the top of the tube.

There was a camera piggyback bracket on the rear cell and a corresponding aluminum block on the corrector assembly. The piggyback bracket in the rear and the block in the front were connected by a plastic (reinforced with fabric threads) strap, which I recalled was intended to be used as a carrying handle, a  handle to help you mount the scope on and remove it from its Vixen Super Polaris GEM mount. Yep, this was an old SP-C8 OTA. While the Super Polaris C8 did go on sale in 1984, the earliest ad I could find showing an SP-C8 OTA with the handle was from 1988.

I seemed to remember the piggyback/handle OTAs as coming a little later than 1984, so 1988 or maybe 1987 seemed a distinct possibility. Which put the scope’s year of manufacture squarely during the visit of Halley’s Comet, a time when both Meade’s and Celestron’s quality suffered. Well, I hadn’t planned to do much with this scope other than take it apart. If I decided to try to observe with it? Some Halley scopes are bad, but some are pretty good.

OK, what gave it its hangar queen status? It was missing its 30mm finder, which must have gone to serve a scope in better health. It did have a pretty plastic (non-locking) corrector cover, which, naturally, fell off the instant I removed the scope from the box. The OTA was missing the plastic cap for the rear port. What else? While examining the C8, as I always do in these cases, I gave the secondary mirror mount a twist. It spun freely. Ah-hah! That was the principal faux pas of this ancient feline.

The rear cell port cover problem was solved with just a minute or two of rummaging through one of Chaos Manor South’s many telescope junk drawers. The rotating secondary assembly? That was a different matter. Might be easy to fix, or it might require some cogitation, if not blood, sweat, and tears.

A little strategizing might be required, but an SCT’s secondary is at heart a simple thing. The plastic secondary assembly (the secondary mounts of some early scopes are metal) of a Celestron (or Meade) scope is inserted through a hole in the corrector plate. The outer face of the assembly with the collimation screws on it is held in place against the lens by its slightly larger diameter. The secondary mirror extends into the interior of the OTA, natch, with the secondary facing the primary.

A slightly conical baffle is attached to the secondary assembly on the inside.  This performs two functions; it reduces stray light and it secures the whole secondary assembly firmly in the corrector. On Meades, the baffle is threaded and screws onto the secondary assembly, which is also threaded. If the secondary mount on a Meade scope comes loose, fixing it is just a matter of removing the corrector and tightening-up the baffle. If only it were that simple with a Celestron.

Usually it ain’t. On all the Celestrons I’ve disassembled, the baffle has been glued to the secondary assembly, not threaded in place. Sometimes, it’s fairly easy to break the glue loose. Would that be the case with this one? No point in wondering, might as well find out. I pulled the corrector, being careful to note the position of the little paper centering shims around its periphery.

Twisting the baffle while holding the other part of the assembly tightly had zero effect. Obviously glued down real good, dammit. What to do? I’ve helped quite a few folks solve this conundrum. Sometimes it is as simple as bearing down a bit. Just be sure to bear down somewhere where the corrector will land on a padded surface if it gets away from you. No dice. No matter how hard I twisted, the baffle was not coming loose. Not even with the aid of a pair of strap wrenches. I felt like if I applied any more torque something was a-gonna break.

OK, idea two. I’ve sometimes had success in breaking the glue loose by the application of alcohol with a Q-tip. No matter how much I used, or how long I gave it to soak, nothing changed. Still stuck. I’ve occasionally been tempted to try some WD-40, but the prospect of cleaning it up, and maybe damaging plastic has always restrained me.

Hokay, lets go nuclear. For the most afflicted patients, what I’ve done is subject the secondary to several freezing-warming cycles. I put corrector and secondary in the freezer for 15-minutes and gave it another try with the wrenches. Nope. Repeated that several times, and, finally, the dang thing budged. Shortly I was holding the two halves of the secondary assembly. Some amateurs wonder if this freezing-warming might break or crack the corrector, but that has never happened to me and I’ve not heard of it happening to anybody else.

Anyhoo, with the secondary apart I could set about repairing the rotation problem. Before I did that, I checked the surface of the mirror. It looked OK. If it had not been? I generally counsel against cleaning SCT mirrors, but if the secondary mirror in this old puppy—err… “kitty”—had been dirty I might have had a go at it with distilled water. It didn’t need it and neither did the primary, which, in typical SCT fashion, still looked surprisingly good after all those years.  The corrector did need cleaning, and I did that in my usual way with blue Windex, white (no lotion) Kleenex, and canned air.

Now for the fix. Since this Celestron secondary mount/baffle was glued together, it would, alas, require more glue to put it back together. The glue I chose for Agnes Gooch (which is what the C8 whispered her name was) was good, old Superglue. It holds firmly, but in my experience is also sufficiently easy to break loose from plastic should you need to later. I know it’s probably not the best adhesive for plastic, but it doesn’t seem to do bad things to whatever sort of plastic Celestron uses.

Before I glued it down, I’d need to get the secondary’s rotational orientation correct, which is very important with both Celestrons and Meades, and which was easy to do with this scope. The brackets on the OTA’s top were a good indication of “up,” and all I had to do was rotate the secondary mount till its serial number was right-side up and correctly oriented relative to them. The rotational position of the corrector is indicated by a tiny engraved serial number, which goes at 3 o'clock (and which also indicates you've got the correct side of the corrector facing out if you can read the numbers correctly while facing it). Glue time. I won’t say I did the neatest job in the world, but I did OK, and after the Superglue had set for 24-hours the secondary was firmly locked in place.

OK, Agnes was off the operating table. What now? Collimation. But to collimate, I’d have to mount her on, well, a mount. Should I order a Vixen format dovetail and put her on the CG5? That would work…but…then I’d have three C8s for the CG5. What if…what if… I put Agnes on the Ultima 8’s old fork? Two birds with one stone. That would provide a heavy-duty (emphasis on HEAVY) mounting for the OTA, and it would help me stop feeling bad about letting that wonderful ultima mount gather dust upstairs in Chaos Manor South’s Massive Equipment Vault.

Naturally, I had retained the screws that had attached Celeste to her fork. Hell, I even knew where they were. It was the work of just ten minutes to get the tube on the fork. In retrospect, I should have taken my time. I should have hunted down the long hex wrench needed to spread the fork’s arms apart. I skipped that step, which resulted in me putting a right good scratch on the tube in the process of getting it mounted. A little black automotive touch-up paint fixed that later.

Hokay, tube on fork. What did I think of Miss Agnes, the faux Ultima 8, the FRANKENSCOPE reanimated with dead SCT body parts? I missed the rear cell handle on my real U8 OTA, but balance seemed fine, and despite the wacky handle, the combo looked pretty good.

Since, amazingly enough, it was clear that evening, into the backyard for a collimation run with Polaris we went. Although I use Bob’s Knobs, which I love and swear by, on Celeste, I must admit Agnes’ Allen collimation screws are a close second and far more pleasant than the Phillips screws on newer Celestrons. I dialed-in Agnes without a hitch, and from what I could tell from a quick star test in skies that were growing increasingly unsettled, her optics were at least OK. Before I could learn more or look at anything else, a great river of clouds poured in just slightly behind schedule.

After that? Nothing. Nothing for over three years. I did the photo shoot for Choosing and Using a New CAT, even pulling Agnes’ primary (those pictures wound up on the cutting room floor, I’m afraid), she was put back together, the book was published, and Frankenscope went upstairs to sit. Why? Celeste on her CG5 and the fork mount NexStar 11 GPS worked so well I didn’t see why I’d want to lug out a dumb old manual SCT. Should I sell her? Give her away? I considered the options, but never got around to deciding whether she should stay or go.

Until one recent evening just after the Spring Equinox. An email from Possum Swamp Astronomical Society’s new President, Martin, said we were “go” for our planned sidewalk astronomy outing on Astronomy Day 2012, the last Saturday in April. I was pleased to hear that, since I actually like doing public outreach. The only question was “Which telescope?”

I’ve tried several public star party solutions over the last few years. My 3-inch f/11 refractor Eloise on her Synta AZ-4 mount has worked well several times. She LOOKS LIKE A TELESCOPE, is a breeze to transport and set up, and gives surprisingly good views of the bright objects appropriate for the kinder. Single down-check for Eloise? No drive. Even at fairly low magnifications it’s a pain to have to re-center objects between “customers.”

OK, then how about the RV-6 Dynascope Newtonian who has been my nominal public-outreach scope for a while? Exquisite optics in the long focal length 60s Newtonian mode. I use her for a variety of public outreach activities, including with my college students and public school pupils. The only problem? For a venue like the one we’d be at for Astronomy Day, a big outdoor shopping mall? Many of our observers would no doubt be the littlest of little folk, and it is impossible for them to get at the eyepiece of a long Newtonian.

Yeah, I know there are dodges. You can bring along a step-stool. But I worry about the wee ones taking a nosedive off one or somebody tripping over one, even in the (at best) semi-darkness of the shopping center. The tiniest observers have to be held up to the eyepiece by their parents (don’t you lift ‘em up; in this day and age leave that to parents), and most of ‘em don’t see a blessed thing.

What is the perfect public star party scope? There ain’t one, but an 8-inch SCT comes close. One is reasonably portable, the eyepiece height is perfect for all but the littlest of the little people, most have good drives, and at f/10 you can pull in some sweet images of the Moon and planets, which is about all the kids and their parents want to see. Coulda been Celeste, but I really didn’t want to fool with a big battery and a go-to alignment just to show off Saturn. “Oh, Agnes!”

 Agnes Gooch it would be, then. I’d need to check her out to make sure she was ready to go, of course, which I did that very night. First up was a little cleaning to get rid of several years’ accumulation of dust and dirt. After an application of Pledge to her OTA, Missy was looking right fine. It was then that I remembered I’d forgot to remove the nine-volt battery that powers her drive when I’d stored her upstairs. Hoped it hadn’t leaked. It hadn’t. I trashed it and installed a new bunny battery.

Flipped the switch from o-f-f to o-n, and the correct light came on. Hunted up the HC, plugged it in, and the drive responded to east and west button mashes as it was supposed to. I could tell by engaging the little-known faster slewing speed some of Celestron’s older scopes feature: hold down E or W and press the opposite button and the drive will ramp-up in speed. I let the scope track for a half hour or so to make sure all was well—it seemed to be.

All that was left was installing a finder. That could be just a Telrad. I had forgotten I’d done so, but at some point I’d bought a Telrad base and applied it to Agnes. Maybe for the photo shoot. A Telrad would be OK…but…what about Celeste’s original Celestron finder scope, a lovely Japanese 7x50 illuminated job? Celeste now sports an Orion RACI right-angle finder, so the original finder scope and rings were sitting unused. In ten minutes, they were on Agnes and she looked prettier than ever. Miss Dorothy was impressed.

Astronomy Day finally arrived, and that afternoon it was time to round up Agnes’ pieces and parts. Diagonal? I wanted to use a 30mm wide field eyepiece, an 82-degree apparent field 2-incher, a “Birdseye,” which Herb York used to sell at Anacortes, so I’d need the 2-inch William Optics Diagonal. Other eyepieces? I figgered I’d bring the Orion Expanses. Nice, wide fields and large eye lenses that are easy for younguns to look into.

Why don’t I use my Ethoses at public outreach events and give the kids the best experience possible? Well, I’ve waffled back and forth on that over the years, but in addition to not wanting to scrape teen mascara and lollipop residue off my TeleVues, I find that in an f/10 scope the Expanses deliver wonderful views. Mom and Pop and Bud and Sis ain’t gonna know the difference, anyways.

At 6 p.m. it was time to load up the 4-Runner and make tracks for the shopping center just across the bay in the little town of Daphne. Loading was not bad. Yeah, I now recalled just how heavy the combination of Celestron’s original rubber coated field tripod and heavy duty wedge was, but it was not too painful. And the fact that I didn’t need to lug a jumpstart battery and the pair of counterweights the CG5 requires meant loading went fast: scope/fork, tripod/wedge, little camp table, eyepiece box, and I was done.

Out at the Eastern Shore Centre, I bopped on over to Barnes and Noble for a copy of Sky at Night Magazine while waiting for the Sun to get low enough for me to give passersby a peep at the crescent Moon and the three bright planets on display. Before long, dark shadows began falling and I got Agnes on her wedge, which I pointed roughly north, but did not obsess about.

The good old PSAS is a small club, but we were able to muster six telescopes for this occasion, just enough to handle the curious little families that began to wander by the fountain area where we were set up. One and all, they wanted to know if this was SOMETHING SPECIAL. I told ‘em we’d soon be giving them good looks at the Moon and Saturn, which caused quite a stir. I hoped I’d be giving them good looks. Beyond collimating on Polaris, I’d never looked through this scope. “Pretty Moon or a custard pie?” that was the question.

Pretty Moon. At f/10 in the 30mm, Selene’s whole lovely self was visible, but with enough magnification to show considerable detail. The kids loved Luna. The parents loved Luna. I loved Luna. As we cruised from the Moon, to Saturn coming up in the east, to Mars overhead, to Venus in the west, I became more and more impressed. The images in this old scope were as good as…as good as…

Well, hell, the images looked as good as those any other 8-inch SCT, including Celeste, would have yielded under similar conditions. The Cassini Division was easy to see and so was some banding on Saturn’s disk. Mars gave up detail despite his shrinking size. Venus was a sharply defined crescent that literally tugged at my heartstrings, bringing wistful memories of gazing at her glowing face from Mama and Daddy’s backyard.

I was convinced this was the beginning of a beautiful friendship. No doubt the RV-6 will still get plenty of time under the stars with the older kids, but the C8 is definitely the IT girl for the little folk. The excellent (Byers) drive made observing with her a joy and the height of her eyepiece was just right for all but the wee-est of the wee brigade.

Did I miss the go-to of the CG5? Nope. At this venue we were limited to the Moon and bright planets by light pollution, and even at the public schools’ Environmental Studies Center, where we do two public events a year, “deep sky” means “M13, M42, and maybe M35,” all of which your old Uncle can still find the old fashioned way.

Best moment this Astronomy Day? One skeptical appearing young woman went to Agnes’ eyepiece for a look at Saturn after some urging by her buddies. She looked, and she looked, and suddenly she began screaming with joy—literally. One of the mall cops actually came over to see what was wrong. There was nothing wrong. This person had just had her eyes opened in a new way. Don’t like doing public outreach? I suspect you’d have changed your mind if you’d been with me on this night.

Anyhoo, I was back home at Chaos Manor South by 9:30 p.m. I left Agnes in the front parlor temporarily while I rounded up that consarned bottle of Yell for a wee nip, muchachos. I figured I probably ought to haul her back upstairs, but I didn’t, not right away. In fact, I put her fork/OTA back on the wedge so I could admire her. Not bad, not bad at all for a patched together Frankenscope of an SCT, I reckoned.

Next Time: (more) My Favorite Fuzzies…

Comments:
The ribbed rear cell goes very well together with this fork, aesthetically. I may be wrong but I believe this combination was actually offered by Celestron at some point. I wish they hadn't abandoned this "industrial" look for something somebody at the company probably thinks is more family-friendly.
 
hi... I have a 14 inch celestron telescope Im trying to sell. Illness forces sale. serial number - 648 9 . it is a early model dating to at least to the early 80's when I got it.
Hotcoffeein510@aol.com
for replies or directions..
thanks


 
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