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Celestron C90 - 1000mm f/11 ?

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#1 ponz

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Posted 14 January 2013 - 06:35 PM

My girlfriend dug this up from her basement. It has a tiny finder scope on it along with a Hybrid Diagonal #94 106 and Celestron 25mm SMA 1.25 Wide angle eyepiece.

Is it good for anything?

Can I utilize it in any way with my new Skywatcher Pro ED80?

Thanks - Ponz

#2 bremms

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Posted 14 January 2013 - 07:15 PM

Yes, they get some bad press, but some have good optics. I had one that I sold to a friend that gave nice images. It is super compact, you can get a 1.25 inch back, but hey are a little hard to find.

#3 CharlieB

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Posted 14 January 2013 - 10:54 PM

If it's like this one, it's a keeper. Was there a mount with it? It's a good lunar, planetary and double star scope. The longer focal length will complement your ED80. Or you could look at it as trash and send it to me...

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#4 rmollise

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Posted 15 January 2013 - 07:51 AM

My girlfriend dug this up from her basement. It has a tiny finder scope on it along with a Hybrid Diagonal #94 106 and Celestron 25mm SMA 1.25 Wide angle eyepiece.

Is it good for anything?


Thanks - Ponz


It is good for quite a few things. You can read my thoughts on the little guy here...

#5 ponz

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Posted 15 January 2013 - 07:52 AM

If it's like this one, it's a keeper. Was there a mount with it? It's a good lunar, planetary and double star scope. The longer focal length will complement your ED80. Or you could look at it as trash and send it to me...


Similar. Mine is all black with a different focus ring.

#6 ponz

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Posted 15 January 2013 - 08:04 AM

My girlfriend dug this up from her basement. It has a tiny finder scope on it along with a Hybrid Diagonal #94 106 and Celestron 25mm SMA 1.25 Wide angle eyepiece.

Is it good for anything?


Thanks - Ponz


It is good for quite a few things. You can read my thoughts on the little guy here...

Thanks Rod - I did re-grease it a few months ago, but haven't given it a fair chance yet!

Ponz

#7 actionhac

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Posted 15 January 2013 - 12:25 PM

I absolutely love my C90.
I even went as far as buying another one just in case I wear out my present one in the time I have left here. I did the same with my Converse all-stars.
The amazing thing about the C90 is how Celestron managed to get the little Mak to work so well visually at f11. I thought Maksutov's needed to be around f15+. Good for us though, because it makes the C90 much nicer to use. I have a 90mm f13.9 Mak and it has a much narrower field of view. And also because the 13.9 has a smaller secondary it also has a smaller baffle tube, too small in my opinion I'm having trouble controlling stray light on brighter objects.
So yes I do love the C90 and thankfully the are not very expensive in comparison to anything else in the same optical quality and aperture.

Robert

#8 terraclarke

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Posted 15 January 2013 - 02:06 PM

Robert, It sounds like you feel about your Converse All Stars like I feel about my black Converse One Stars ;)

"Stars" = not off-topic ;)

#9 jezz

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Posted 15 January 2013 - 02:35 PM

I was given a brand new one with case in the 90's for xmas one year - Armourcoated or something to that effect - 2nd worst scope I ever owned - sold it shortly thereafter.

#10 actionhac

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Posted 15 January 2013 - 04:01 PM

Robert, It sounds like you feel about your Converse All Stars like I feel about my black Converse One Stars ;)

"Stars" = not off-topic ;)


I was afraid they might stop making them, and my feet are molded to the Converse, its hard for me to wear anything else.
They really are not a very good shoe though, no support. But then the all-star was designed for basketball and worn for only a short time.

Robert

#11 actionhac

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Posted 15 January 2013 - 04:14 PM

I was given a brand new one with case in the 90's for xmas one year - Armourcoated or something to that effect - 2nd worst scope I ever owned - sold it shortly thereafter.


This is very common feeling I've noticed. The C90 through history has had a mixed review. I really think more people hate than like the scope.
It would be interesting to do a survey and find out exactly what the likes and dislikes are.
I personally don't like the camera lens style helical focuser for astronomy, for anything else its a nice fast focuser and Its great. Otherwise I think the C90 is the cats meow. But then I've owned 5 Corvairs so what does that tell you?

Robert

#12 Mike Lynch

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Posted 15 January 2013 - 04:32 PM

And if you need an instruction manual, "Littlegreenman" has one for sale at the CN classifieds now! :jump:

Mike Lynch
Frankfort KY USA

#13 Joe Cepleur

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Posted 15 January 2013 - 05:48 PM

1.25" visual back for a C90? Piece o' cake!

http://www.cncsupplyinc.com

Click the link in its left sidebar for this item:

Rear Port Adapters (Visual Backs) ETX/C90 (34mm)

#14 Glen A W

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Posted 15 January 2013 - 05:55 PM

WE had this problem last week, but I was able to find two 1.25 visual backs which were stamped by Orion.

I like the scopes well, but the focusing, while it works well, does cause problems if your tripod is not real sturdy. Overall, the image is pretty dim, too, but the scopes are tough and fun to use.

#15 Joe Cepleur

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Posted 15 January 2013 - 07:23 PM

The misgivings I had in assessing the only C90 I've ever used appear to be quite common, along with enthusiasm for having so much optical power in so small a package. I wish I could attend a big star party of only C90s. I'd love to look through a lot of them, to see whether any have truly stellar optics, or whether they all feel so compromised as mine. Given the occasional wild enthusiasm reported on these forums and Uncle Rod's blessing in his blog, some C90s must be truly wonderful.

Today through my borrowed C90 and a 25mm Plossl (50x), I watched three juvenile bald eagles on the ice a mile away across the lake. I was not yet dressed to go outside, so this was additionally through a window and the screen porch outside. Even with the screen being especially damaging to the image, I was impressed that anything so little gave such a good view. Contrast? Feh. Clarity? Through a screen?! Good enough. Honest. Even if mine were among the best of them, so compromised a scope would still offer effortless portability and a far better view than the naked eye.

So, is it good for anything? You betcha! Especially when it came to you free out of your girlfriend's basement. It may not replace your 4" Unitron or your coveted Nippon Kogaku, but you would not lug them where you'd effortlessly float the C90.

I suspect that birders love the scope more consistently than astronomers. The same C90 that feels compromised on the stars and lacks the resolution to be truly pleasing on distant objects excels on close-ups of birds that are already close in bright daylight. Before I got the C90, I twice watched those bald eagles eat lunch in a tree not 100 feet from my window. Imagine that view! Coulda counted the blood vessels in the predator's eyes, or seen every last filament of his feathers.

Now if I could only decide how much to offer on my borrowed C90. It's portable and serviceable, but I suspect not the finest of its kind.

#16 johntrob

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Posted 15 January 2013 - 07:46 PM

As they say, Beauty is in the eyes of the beholder. I love my C90, for many of the reasons Joe stated.

#17 Geo.

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Posted 18 January 2013 - 06:45 PM

Now if I could only decide how much to offer on my borrowed C90. It's portable and serviceable, but I suspect not the finest of its kind.


I've picked them up with "issues" (usually loose baffle tubes) for as little as $40 and sold them for as much as $275 (love the French!). Orange tubes are going in the $90-175 range and black tubes $75-$125. The prices are very dependent on the presence of OEM accessories such as the finder, eyepieces, diagonal and Barlow. These have to be present to get into the upper range in prices.

#18 Joe Cepleur

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Posted 18 January 2013 - 07:20 PM

Thanks for the help!

Mine is a black tube. It has the 8x20 finder with cross hairs intact, and the foam-lined, hardshell case, but nothing else. The seller admits there is something odd with its optics. I suspect they may be serviceable, but not the finest ever made, and that better accessories may help at added cost. This puts the scope on the low end of the scale.

#19 Rand Barthel

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Posted 18 January 2013 - 09:14 PM

I bought a C90 astro scope just like the one in the OP back in about 1981 or 82. I thought it might be possible to stargaze with it from the roof of the apartment building I was living in in Cambridge Mass. That proved to be largely wishful thinking, but I found I could also use it as a spotting scope for birdwatching (remove it from the astro mount and put it on a photo tripod). I also used it as a long telephoto lens. I found, once I equipped it with an equatorial wedge and tripod, that it was possible to use it on planets, the Moon, and the more prominent deep-sky objects. The smallness of the mount and the lack of clearance between the mount and the back of the scope made it hard to observe anything near the north pole because I had trouble getting my face and eyes positioned to look through the scope. For astro uses my RV-6 is clearly a better proposition, but it's hard to be more grab-and-go than a C90.

#20 Joe Cepleur

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Posted 18 January 2013 - 10:12 PM

Thanks, Rand;

The C90's one-armed bandit astro mount was tempting to look at, something every grab-and-go enthusiast might covet, but your experience suggests there was good reason so few were sold, and perhaps so many deforked. I've though of finding one, just because they are so cool. Functionally, would you say I'd be better off with a good alt/az mount than an original Celestron one-armed fork?

#21 Rand Barthel

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Posted 06 June 2013 - 11:03 PM

I just realized I never responded to your question. You can actually use the one-armed fork in alt-az mode by skipping the equatorial wedge. The drive base makes it quite steady as a table-top scope, and you can easily grab the whole assembly by the fork arm and carry it in one hand. I'm not sure what's available by way of an alt-az mount that would work, unless you used a hefty photo tripod and the tripod screw socket. I think the fork in alt-az mode would be better because it has locks and slow-motion controls on both axes.

#22 JonH

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Posted 07 June 2013 - 01:01 AM

Following the bump, I thought I would chime in too. For birding, hiking or those impromptu surfing trips, I use a C90 with a manfrotto camera tripod, it has three axis rotation and its relatively easy to get the scope pointing to zenith. Like Rand said earlier, the clearance at the back of the scope is a bit tight but if you have the original diagonal and a barlow you can get quite comfy. I may have missed it somewhere else in the thread, but just so you know The C90 has an attachment thread on its base and will fit onto just about any camera tripod.

With regards to C90s and reliability, I have two, an orange tube from the seventies and one of the black rubber armor jobs from the nineties (I think). The orange tube gave awesome star tests and performance right from the start. The later scope was a bit of a dog, but came good following some hints from Rod (it had a loose focuser).

#23 Jon Isaacs

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Posted 07 June 2013 - 06:57 AM

Since this thread was bumped, I will take the opportunity to comment on a C-90 I bought a few months ago. It's a black one, it came with a shield, a 0.965 back and a 18mm eyepiece of some sort.

It provided decent terrestrial views but viewing double stars showed it to be out of collimation. I looked at the web, fooled around with it doing the things suggested... Nothing really helped, the views were not bad, just not what I expect...

I took the scope further apart, removed the gumpucky that held the mirror to the baffle and attempted to collimate it... big mistake...

It's in a box now on the shelf.

Jon

#24 greju

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Posted 07 June 2013 - 01:12 PM

Just like all scopes of that era you can get a good one, a great one or meh. If you can get used to the "focuser" and if it has decent glass they are a lot of fun. Oh, and pretty to look at. ;)

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#25 Joe Cepleur

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Posted 07 June 2013 - 09:18 PM

I think the C90 is the cats meow. But then I've owned 5 Corvairs so what does that tell you?



It tells me that your C90 would break apart exactly where the visual back meets the primary mirror housing in the event of an accident.






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