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Upgrading from a Celestron 'Cometron'

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#1 chaoscosmos

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Posted 06 February 2013 - 11:48 PM

Hey all.... I've got a Celestron 'Cometron' that I've gotten out of its box recently- have had it for awhile and don't even recall how I got it, but it's a 62mm refractor with a 300mm focal length. I took it off its table top tripod and put it on a Leitz Tiltall camera tripod, and took it out the other night into the backyard. It showed some good views of Jupiter and 4 of its moons.

I'd like to upgrade it a little bit, and get a mount I can tilt to the zenith (the Tiltall won't go that far). I think I want an Altazimuth mount. Are there some of these that are pretty rock steady and easy to move in one motion? I'm thinking I'd like to get a scope that's moderately wide field, with an aperture somewhere in the range of 80 to 120mm. I'd prefer to keep the cost of the set-up at around $1000 or less. I could go higher except that I want to follow up sometime, maybe this year, with a 12" Dob.

Any recommendations? I'd like something that's pretty good build quality, so I'd probably sacrifice aperture for that, with a solid mount and quality optics. I know it's a slippery slope I'm getting into because I do like quality stuff (I own Leica and Hasselblad cameras), but I do have a budget.

I am planning on going out to a star party to check stuff out, but that might be a month away, and I'm sort of getting the itch now.

#2 BigC

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Posted 14 February 2013 - 02:48 PM

An Orion 120ST and mount comes to mind.
Probably similar in other brands.
A short 120mm has ample aperture to keep things really interesting and in f5 to f7 gives pretty wide field;CA may be evident unless you get an ED-glass scope.

#3 Jon Isaacs

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Posted 15 February 2013 - 06:54 AM

I'd like to upgrade it a little bit, and get a mount I can tilt to the zenith (the Tiltall won't go that far). I think I want an Altazimuth mount. Are there some of these that are pretty rock steady and easy to move in one motion? I'm thinking I'd like to get a scope that's moderately wide field, with an aperture somewhere in the range of 80 to 120mm. I'd prefer to keep the cost of the set-up at around $1000 or less. I could go higher except that I want to follow up sometime, maybe this year, with a 12" Dob.



Hi:

A couple of thoughts:

- I am not sure what the problem is with the range of the Tiltall. If I am mounting a scope on photo tripod, I mount it "backwards", that is the handle/lever in front rather than in back as one does with a camera. This generally eliminates any conflicts that prevent viewing the zenith.

As far as mounts, the Vixen Portamount and the Astro-Tech Voyager are proven alt-az mounts that are stable and offer slow motion controls so once you have located your target, you can crank up the magnification manually track the object.

As far as scope, what do you hope to look at? An 80mm ED like would be a nice all around scope. Larger achromats would provide more deep sky performance at the expense of the planetary views.

Jon

#4 watcher

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Posted 15 February 2013 - 08:14 AM

Everyone should have a nice 4" refractor. How about this scope on this mount. Not an alt az mount, but I think EQs are better if you do any higher magnification observing.

#5 hottr6

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Posted 15 February 2013 - 08:29 AM

Don't sell the Cometron! They are a sweet little 'scope, and inch for inch, will provide better views than Chinese glass.
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Cometron on the right.

Shane in gray-zone NM

#6 REC

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Posted 15 February 2013 - 10:26 AM

I have the 80mm version of this from the 80's...fun little WA scope. It has a "v" listed on the plate and I think it means Vixen glass vs. the later Chinese models. Paid only $50 back then when the Comet craze fizzeled.

#7 chaoscosmos

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Posted 15 February 2013 - 11:10 AM

Thanks Jon.... Why didn't I see that? Goes to zenith now with lever/handle on the opposite side.

As far as scopes, I'm looking for a used NP-101 or TV85, and also looking at scopes the next level down in price. I'm somewhat of a beginner but as a photographer am also quite visually aware..

#8 chaoscosmos

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Posted 15 February 2013 - 11:14 AM

By the way, with the Cometron, do you guys know if it can be adapted for 2" diagonal or eyepieces?

#9 Jon Isaacs

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Posted 15 February 2013 - 11:21 AM

Thanks Jon.... Why didn't I see that? Goes to zenith now with lever/handle on the opposite side.



There are some other tricks you can play if you have a three axis tilt-pan head. You flip the top axis 90 degrees and mount the scope "side-saddle." The advantage of this is that the telescope balance does not change as you move from the horizon to the zenith. If the scope is mounted on top like a camera, as the elevation increases, the balance shifts back and it takes more and more friction to hold it in place. With a 60mm F/5, it's not much of a problem but with larger scopes it can be.

Jon

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#10 Eddgie

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Posted 15 February 2013 - 12:29 PM

I'd like something that's pretty good build quality


I am not trying to be anything but constructive here, though it may not sound that way to you...

I guess my question would be "What to you constitutes good build quality?"

Todays ED scopes generally have absolutely superb optics. You can spend a lot more money, but not get meaningfully better optical quality than a Synta 80mm or 100mm ED scope.

I have not encountered any of these where things like lenses were falling out, so from a design standpoint, they will be built well enough not to fall apart, and usually are quite well made and very nicely finished.

The biggest difference comes in the area of focusers, and here, while there is indeed a bit of a difference, it is not as much as it used to be, and not as much difference between a decent quality Crayford and a Feathertouch. If you buy a Tak or something, sure it will have a nice focuser, but for half the price, you could buy a 100mm or 120mm ED scope and put a Feathertouch on it.

Only you can define what an acceptable level of build quality is, but even very moderately priced ED scopes have quite excellent build quality these days.

So, what in your own mind constitutes "good build quality?"

Even if you are more concerned with Optical Quality than just "build quality", the modern ED scopes seem to be coming from Synta with outstanding optical quality.

Stellarvue is a US company that is also consistently shipping excellent quality optics and perhaps are coming with slightly better focusers (not that a lighter focuser would have a poorer build, but might not handle heavy eyepeices well. Does this matter? Will you be using a 31mm Nagler? How heavy is the camera you intend to use?

To get a full up system for less than $1000 (decent mount and telescope with high quality optics) you may find that the Synta products are going to be your very best bet. Not only are they priced well, the quality build quality (optics, finish, focuser, etc) is quite good by anyone's standards.

#11 chaoscosmos

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Posted 15 February 2013 - 01:17 PM

Oh boy, I guess that $1K has been revised upward a bit since I first posted. Along with a used TV, I'm looking at Stellarvue, Explore Sceintific, and other options. Hoping now to avoid 5K when all is said and done with mount, eyepieces, etc. As far as build quality, I want something that's smooth and solid and that I don't have to fight against or fix. Like many here, I like well crafted tools... also something that can be sold easily if I get out of the hobby or find I have other obligations.

Thanks again Jon, I'll check side saddle out later.

#12 Jon Isaacs

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Posted 15 February 2013 - 01:19 PM

I have not encountered any of these where things like lenses were falling out, so from a design standpoint, they will be built well enough not to fall apart, and usually are quite well made and very nicely finished.



There is a large variation in fit and finish of the various ED scopes. All are adequate, some are exquisite. Scopes like the ED-80 and ED-100 use cast parts with a minimal amount of machining, tubes that are probably rolled and not machined. They work but they are not a thing of beauty. They are very similar to the Synta Achromats, Spartan is the word I use.

One pays more, the fit and finish is better, the dew shield will slide, the paint will be very well done but in my experience, there will still be issues, Crayford focusers are always problematic.

In terms of fit and finish, in my mind, the TV-85 and the NP-101 are about as good as you can get. Honestly, I think my William Optics 80mm Megrez II FD with its white paint and gold trim is prettier than my NP-101 but in terms of fit and finish, mechanical quality, (and optical quality) the NP-101 at the next level, everything is well thought out and it just works.

Optically, the Syntas are good for what they are, a 100mm F/9 doublet. A scope capable of nearly 3 degree fields but with some field curvature. I suspect that a photographer will probably appreciate the clean wide field views that the NP-101 provides. And maybe at the high magnifications, there is the apparently perfect color correction.

Consider the Cometron, 60mm F/5 and if I am not mistaken a 0.965" focuser. Nearly a 4 degree TFoV is possible. The NP-101 is capable of almost a 5 degree TFoV and it is free of field curvature.

I am a big fan of the NP-101 because it is essentially perfect at doing the things I do with a 4 inch refractor.

But they are expensive, if a 36 inch long OTA rather than a 26long OTA is OK, if some field curvature is acceptable, if a 3 degree TFoV rather than a 4.9 degree FoV is OK, a used Orion ED-100 is certainly far more affordable and a fine scope in it's own right.

Jon

#13 hottr6

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Posted 15 February 2013 - 01:59 PM

onsider the Cometron, 60mm F/5 and if I am not mistaken a 0.965" focuser.

My CO-62 came with a 1.25" R&P focuser (see photo above), and a 6x30 finder. The finder is almost as big as the main OTA. :foreheadslap:

Shane in grey-zone NM






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