Sunday, June 03, 2007


How Do You Mount a CAT?

That is, what kind of a mounting do you want for a catadioptric telescope; especially an SCT? For years I’d have said “fork it.” My inclination heretofore has been to buy SCTs as packages complete with integral fork-mountings. Until recently. I still use the forks, but my love affair with ‘em is definitely over.

Why is that? Well, I’ll tell ya, muchachos, it’s largely a consequence of Your Old Uncle Rod getting up there into advanced middle age. Until recently, though, I saw no reason to change my scope buying and using habits. I’ve had a Celestron Ultima C8 ("Celeste") for years. No, she ain’t got no goto computer gee whizzery, but for the longest time I nevertheless considered her the last word in 8-inch SCTs. The U8 integrated a good OTA with a drive base containing a sweet Byers worm set, a DC drive, and PEC. To ride on this drive base, the U8 nestled in what was probably the heaviest fork ever furnished with an 8-inch SCT.

The end came one cold November star party. I had forgotten what it was like to use a non-go-to fork scope on a wedge (in the old days, a non-go-to scope had to be tilted over on a “wedge” for polar alignment purposes in order to track the stars). It was cold out on that observing field and I was spending a whole lot of time either kneeling on the icy ground or with my body entwined around the wedge like the gull-derned India rubber man at the fair. My contortions became especially painful when I wanted to view far northern targets. The next morning? I was flat stove up.

My solution, as I’ve recounted here before, was to buy a Celestron CG5 German equatorial mount (GEM), snatch the Ultima 8 OTA off her fork (which I’m storing in Chaos Manor South’s Massive Equipment Vault for old time’s sake), and keep on truckin'. What was ground-breaking for me, though, was not that the CG5 worked surprisingly well, but that it opened my eyes to a forkless kind of astronomy. Yes, I still use a fork mount Nexstar 11, but it's a computerized scope and it’s very comfortable to work with set up in alt-azimuth mode

What makes the GEM alternative “better”?
Now, don’t get me wrong, True Believers, sure, my heart goes pitty-pat when I see a fine C14 Orange Tube, and pittypats even more in the presence of a Blue and White C10 or C16, but for me, the fork, I’m afraid, is yesterday. Now I spend my nights dreaming of obscenely huge Losmandy Titans, monstrous AP1200s, and humongous Mountain Instruments GEMs. I mean, what more can you ask for? More adaptability (which is what we SCT users are always talkin’ about as a hallmark of our favorite scope design) coupled with the ability to spend more dollars on more toys. Don’t get much better than that, does it?

Gawd I Wish I had Da Money!Until then,well I'll be forked dead in da -ss!!!!
Gawd! I wish I had da Monies!Until then ,I'll be forked,ded in da -ss!!!
Sorry for the repeat!
Dr. Brian Long brought one of Columbia State Community College's 12" Meade alt-az goto telescopes to a star party a few weeks ago. The OTA plus fork part is over 100 pounds. Grunt! That is well above my lifting capacity. I've got my C8 on a GEM and love it. That is Columbia State Community College in Columbia, Tennessee, BTW.
I really love your writings Uncle Rod!!! Always cool to read texts from you. Still laughting about "forkectomy"!!!!
100% Aggree with you for the GEM: I have a Vixen GP with my C8 and it's fine!!! I just put the mount/tripod on the right shoulder, the OTA bag in the left hand, the accessories back-pack on my back and I'm ready to walk 200m to the darkside of my building "public" garden! With a forksystem I would have to do 2 trips and let some expensive stuff outside.....

Clear skies from Paris!!!
Hey Uncle Rod, you convinced me to get a GEM mounted SCT in the future. I now realised that with a GEM, the whole assembly has a higher portability comparing to the fork mounted assembly. Do you find polar alignment time taking?
No, I really don't. Not with the Celestron GEMs, anyway. Aim the mount roughly at Polaris, do a normal go-to alignment, hit "polar align" in "utilities" menu, and the scope slews to where it thinks Polaris should be given a good polar alignment. You then use the mount altitude and azimuth controls to center Polaris in the eyepiece. The resulting alignment is good enough for all the CCD imaging I want to do (at short focal lengths, anyway).

Only drawback? Once you complete the polar align procedure, you do have to re-do your go-to alignment (you've moved the mount), but that's not a huge pain...

Unk Rod
I love my GEM (MI-250), but I will more likely always keep my first scope that I purchased after 30 years away from the hobby. My Celestron N8GPS sets up in 5 minutes for alt-az viewing. This is THE scope that I drag out for public star parties. It always puts the eyepiece in accessible locations. A kitchen stool accomodates children or adults. It will always have sentimental value for being the first scope I used to get hooked on my passion, astrophotography.
Hi Unk,

I have a quesiton or two that may be helpful for me and others.

How about side by side vs. piggyback mounting of an SCT and Small refractor? Which do you prefer and why? What are the pros and cons of both approaches?


What's the setup time compared to a "modern" fork mount like the Celestron CPC series for visual?

The dollars involved in *really* getting into photography are frightening. :)
Good post.
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