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Something for nothing: Celestron C90

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#276 Sarkikos

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Posted 27 June 2014 - 03:53 PM

I've never taken apart a Mak or SCT. Maybe somebody here can let you know.

Mike
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#277 hardwarezone

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Posted 27 June 2014 - 08:32 PM

I'll ask again. I'm being told that the corrector plate cell on the front of the C90's OTA can be unscrewed? How does one go about doing that?

Likely rotated with a special tool that goes into the 2 hole.
There is a little dab of clear epoxy on mine to discourage anybody trying this.

*edit*
I asked a guy who had flocked at least two 127 synta maksutov and he said the front part of the tube can be twisted off , messing with the tiny 2 holes can wreck the scope.

#278 ylem

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Posted 28 June 2014 - 09:34 AM

This thread is 2 1/2 years old, and I finally got mine :)
Picked up the Orion Apex 90, from the clearance page for 159.99 ;)

This thing is cute, can't wait for 1st light, pictures of the the new kitten to follow.

#279 Patricko

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Posted 28 June 2014 - 04:18 PM

I've several of these over the years. All had ok optics, nothing fantastic. They are "cute" and make ok gng scopes as long as the temperatures are not extreme. I laughed out loud when getting the first one with a 32mm plossl, talk about vignetting big time! The plossl has a 27mm field stop while the rear baffle was constricted to around half that. I found that a Meade 26mm 4000 gave the widest fov with fair field illumination.

It did ok on Luna and planets;however, it lost to my 60/1000mm refractor every time on every target except DSOs, mainly globular clusters. I'm not knocking these as they can be very nice under the right skies on the right targets. I found the M45 not to fit in the ~1° tfov. They are lightweight and fun to use once the stray light issue gets worked out. Changing eye pieces can completely eliminate that issue.

#280 Chuck Hards

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Posted 28 June 2014 - 05:34 PM

I have a used orange-tube C90 in-transit, the seller knew very little about it. I'm sure it will need some cleaning, at the very least. Been curious about these scopes for decades. Hopefully it gets here before next week's long weekend, as I won't have much free time to mess with it after that, for several weeks at least.

#281 Quixylvre

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Posted 28 June 2014 - 07:36 PM

Methinks this thread is more about the newer OTA made by Synta, and sold by Celestron as the C90 spotting scope since 2010

#282 Quixylvre

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Posted 28 June 2014 - 07:43 PM

By the way, the corrector cell on my C90 refuses to budge. Do I need to put the scope in the freezer to shrink the metal?

#283 Chuck Hards

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Posted 28 June 2014 - 11:16 PM

Methinks this thread is more about the newer OTA made by Synta, and sold by Celestron as the C90 spotting scope since 2010


There have been posts about all vintages of the C90, it's been interesting to read the comparisons of the old vs. the new. Seems the consensus is that the optics were better figured in the older ones, but the throughput is better in the new. There are outlyers in the data on both ends of the curve, of course.

If I'm impressed with the old one when it arrives, I may start saving my quarters for the new version.

#284 Sarkikos

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Posted 29 June 2014 - 01:26 PM

I've several of these over the years. All had ok optics, nothing fantastic. They are "cute" and make ok gng scopes as long as the temperatures are not extreme. I laughed out loud when getting the first one with a 32mm plossl, talk about vignetting big time! The plossl has a 27mm field stop while the rear baffle was constricted to around half that. I found that a Meade 26mm 4000 gave the widest fov with fair field illumination.


I measured the rear aperture in my C90 - one of the new batch - with a digital caliper. The opening is 16mm.

Mike

#285 ChristianG

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Posted 02 July 2014 - 03:42 PM

By the way, the corrector cell on my C90 refuses to budge. Do I need to put the scope in the freezer to shrink the metal?


A couple of these should do the trick:

http://mobile.walmar...Wrench/21609437

For mine, I enlisted a friend's two hand to hold the tube, and used my own on the cell. Good luck!

--Christian

#286 Quixylvre

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Posted 05 July 2014 - 08:23 AM

Still haven't gotten the primary baffle-tube flocked quite yet, BUT! Last night I was at my parents' place (darker night sky there than @ my house). There was not a single cloud in the sky, and it was bone-dry. PERFECT telescope weather. I managed to find Mars and Saturn, and even split a double. I haven't got any way to take photos with the scope, sadly, but Saturn's rings were QUITE clearly visible. Hopefully I'll have a chance to order some Protostar flock-board soon.

#287 esldude

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Posted 05 July 2014 - 01:12 PM

Still haven't gotten the primary baffle-tube flocked quite yet, BUT! Last night I was at my parents' place (darker night sky there than @ my house). There was not a single cloud in the sky, and it was bone-dry. PERFECT telescope weather. I managed to find Mars and Saturn, and even split a double. I haven't got any way to take photos with the scope, sadly, but Saturn's rings were QUITE clearly visible. Hopefully I'll have a chance to order some Protostar flock-board soon.


Hey, I have had better than you might expect results just sticking a digicam up to the lens, aligning in the viewfinder and snapping a shot. Enough to give others an idea of what I am seeing anyway. Have managed some okay shots with cell phones that have a few control settings on the camera.

#288 kwjohnson

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Posted 23 August 2014 - 04:27 PM

Can anyone recommend a 1.25" visual back for the C90 with compression rings? It would also be great to get measurements of the scope--the widest diameter (minus the finder) and the length (minus the diagonal).

 

Thanks. This thing sounds like fun.



#289 hardwarezone

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Posted 23 August 2014 - 07:14 PM

The c90 is about 12cm at the widest 2 hoops excluding the dovetail and finder bracket protrusion.

Length is 27cm for the tube + 5.5cm for the visual back.



#290 kwjohnson

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Posted 23 August 2014 - 09:09 PM

Hardware zone--got it. Thanks. 



#291 Starman81

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Posted 02 December 2014 - 11:02 AM

$159.99 at Optics Planet - 11% using 11BLACK code comes out to $142.39 with free shipping! Had to post, still a great deal. 



#292 Sarkikos

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Posted 03 December 2014 - 02:45 PM

Yes, these are great little scopes, and that's a great deal you got.

 

I've had two 90mm Maks. The newest was the C90.  Very nice on my NexStar SE mount for grab-n-go with goto and tracking.  It was my default Moon scope.  I had the C90 for a couple years.  The only reason I sold it was because I got a C80ED.  I couldn't justify keeping the C90 after that.  Besides, my scope collection was just getting too big. 

 

Mike


Edited by Sarkikos, 03 December 2014 - 02:46 PM.


#293 Quixylvre

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Posted 06 December 2014 - 12:28 AM

Any tips on where I can get good flocking material, and specific size it needs to be cut to in order to get an optimal fit in the primary baffle-tube? I know some of you here have already done this, and I'm trying to see if anyone already knows the numbers so as to not risk making a mistake and getting a wrong result whilst attempting to calculate the needed measurements myself.



#294 RodgerHouTex

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Posted 09 December 2014 - 09:48 AM

Just picked one up from OPT.  Perfect optics, no mirror slop, and easily split the double-double.  Does 50X per inch with no sweat.  Jupiter looks great.

 

Guess I won't need that Questar after all.


Edited by RodgerHouTex, 09 December 2014 - 09:49 AM.

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#295 jrbarnett

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Posted 10 December 2014 - 10:37 PM

Just picked one up from OPT.  Perfect optics, no mirror slop, and easily split the double-double.  Does 50X per inch with no sweat.  Jupiter looks great.

 

Guess I won't need that Questar after all.

:waytogo:

 

- Jim



#296 Dwight J

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Posted 11 December 2014 - 01:43 AM

Just picked one up from OPT.  Perfect optics, no mirror slop, and easily split the double-double.  Does 50X per inch with no sweat.  Jupiter looks great.

 

Guess I won't need that Questar after all.

Don't let the refractor people know! :lol:  



#297 RodgerHouTex

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Posted 11 December 2014 - 11:49 AM

 

Just picked one up from OPT.  Perfect optics, no mirror slop, and easily split the double-double.  Does 50X per inch with no sweat.  Jupiter looks great.

 

Guess I won't need that Questar after all.

Don't let the refractor people know! :lol:  

 

 

Yea, they're a tough crowd.  But I do like to tweak the Astro-Physics folks about what they pay for 7 inch scopes.   :grin:



#298 Sarkikos

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Posted 12 December 2014 - 10:54 AM



 



Just picked one up from OPT.  Perfect optics, no mirror slop, and easily split the double-double.  Does 50X per inch with no sweat.  Jupiter looks great.

 

Guess I won't need that Questar after all.

:waytogo:

 

- Jim

 

 

Does anyone really need a Questar? :thinking:

 

Mike


Edited by Sarkikos, 12 December 2014 - 10:55 AM.


#299 RodgerHouTex

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Posted 12 December 2014 - 11:27 AM

 



 



Just picked one up from OPT.  Perfect optics, no mirror slop, and easily split the double-double.  Does 50X per inch with no sweat.  Jupiter looks great.

 

Guess I won't need that Questar after all.

:waytogo:

 

- Jim

 

 

Does anyone really need a Questar? :thinking:

 

Mike

 

 

Haven't you heard.  They defy the laws of physics.  At least that what the ads used to say.


Edited by RodgerHouTex, 12 December 2014 - 11:27 AM.

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