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Celestron C90 Registry

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#76 rgreenberg2000

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Posted 24 December 2019 - 10:29 AM

Whoops, forgot that bit! :)  It's a "T" in a circle.

 

Cheers,

Rich


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#77 Masvingo

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Posted 24 December 2019 - 02:22 PM

Thanks Rich, I've updated the C90 Registry.


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#78 RSX11M+

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Posted 27 December 2019 - 01:30 PM

I've been lurking in your "Registries" as a site visitor for quite a while and finally decided to step-up and contribute as a way of thanks.
 
Please add the following C90s to the registry...
  • Orange (Spotter configuration) with Finder and caps
    C90 1000mm F11 MAKSUTOV TELESCOPE
    SN 93787
    Corrector #7032
    C90F11_93787.jpg
    C90F11-93787-cp.jpg
    [image flipped horizontally]

    Accessories:
    • Orange Crosshair Finder 5x24mm ( Japan(-) )
    • Yellow rubber thread cap
    • Black Objective cover
    • Rectangular carry case with handle
  • Black (Telephoto Lens configuration) no finder or caps
    C90 500mm F5.6 MIRROR LENS
    SN 500214
    Corrector #402
    C90F5.6_500214.jpg
    C90F4.5-500214-cp.jpg
    [image flipped horizontally - note orientation inverted compared to F11]

    Accessories:
    • Orion hybrid star diagonal (1.25"x0.963")  (Japan)
    • Celestron 25mm 1.25" Kellner eyepiece (Japan) vintage styling
    • Unlabeled lens, Apparent Barlow or very high mag type.
      It's Ocular opening is 0.228" (5.8mm) across and the assembly is 6.29" long
      There is a loose optic element within the tube trapped by slit expansion rings
      The assembly contains black-lacquered brass and wood components and is misassembled (cross-threaded?)
      There are remains of a label sticker which devoid of print except for "CHROMATIC" (barely discernible)
    • Celestron labeled cylindrical case w/strap for all items (fair-poor condition)
These were obtained separately via eBay. 

Their condition as received was similar - thread grease had migrated over the years and soiled the optics and other surfaces (in and out) with a thin film. This coating attracted any dust that entered via the rear opening. Dust was particularly heavy on the F5.6 - mostly settling on the secondary mirror reflecting surface.

The F11 also had an odor problem. A major problem. Even now, after extensive cleaning, the scope emits an odor similar to mildew. My belief is that an inappropriate grease was used to lubricate the focus threads and got stale or became contaminated biologically. Windex was used on interior and exterior painted surfaces which helped, probably due to the ammonia content.

Optics were cleaned in the standard manner - detergent & distilled water solution, careful cotton ball "dabbing", rinse with distilled water and tech alcohol mix. Repeat as needed then wipe dry with same type cotton.

Thanks to your "registry" I've an idea now when these were manufactured. [perhaps a new candidate for "earliest" C90 F5.6 so far?  ...kinda fun]
 
They will probably become finders for other scopes though they're pretty fun alone and have a good feel I didn't anticipate. The F5.6 was a fortunate find and best matches a vintage C8 I converted with Hyperstar. (C8 Registry entry to follow) 
 

-Cheers!

Edited by RSX11M+, 28 December 2019 - 03:40 AM.

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#79 RSX11M+

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Posted 30 December 2019 - 06:43 AM

Hi y'all. I just came into ownership of an orange Celestron C90, SN 923078. I'd give you that inner number... but unfortunately the dang thing is so covered in grime I can't hardly make it out myself, nevermind get a good pic of it. Here's an imgur album of current state of it. 

Just for the record... I make that unit's optics number to be "669" - didn't see it recorded in the registry.


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#80 Masvingo

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Posted 31 December 2019 - 07:13 AM

Thanks, RSX11M+, for your detailed reports on your two C90s (and also the heads-up for the optics number for #923078), I've updated the C90 Registry which now stands at Edition 5.

 

Yes, #500214 is the earliest F5.6 C90 so far, what's the performance like?  #500467 was reported as having a soft focus and lots of chromatic aberration .

 



#81 Uranotopia

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Posted 31 December 2019 - 07:34 AM

Howdy folks!  I got my first telescope back in 2012, which is when I registered here.......have been in/out of the hobby since then, and recently back in, and discovered I still had my Craigslist C90 that I bought 7 years ago.  I'll be more active here this time around (CPC800 now), and wanted to add my C90 information to this registry!

 

C90 Spotter (Orange tube)

SN#: 99409

Optics#: 7182

18mm eyepiece

5x24mm finder

2.5x barlow

extender

original case

 

Some photos:

 

49263933838_e4e5dd7a93_w.jpg

 

49264590672_a5c67ba617_w.jpg

 

49264399111_7c9586ae3f_w.jpg

 

49263933353_b6dc41babd_w.jpg

 

49264590347_ca37786476_w.jpg

 

Thanks for building this registry!!

 

Rich

Thx for the Images and informations, Rich!

I wish you many good moments and amazing observations with your telescopes, after you reactivated your astronomical hobby!


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#82 RSX11M+

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Posted 01 January 2020 - 11:05 AM

Yes, #500214 is the earliest F5.6 C90 so far, what's the performance like?  #500467 was reported as having a soft focus and lots of chromatic aberration .

Observations:

  • The focus implementation suffers from inherent mechanical design weaknesses-challenges. Thread tolerance variations would manifest as inconsistent optical performance unit to unit, even within the same type and spec.
  • The grease migration (vaporization and redeposition?) which took place in both of my C90s over time, must cause severe optical issues if not corrected.  (Did those reporting aberrations note this too?)
  • Inappropriate Cleaning methods would present further risks.

 

These are my first and only MAKs. I'd prefer a while longer to evaluate and understand them. It would be unfair to draw too many general conclusions based on these vintage examples - having traveled through time in the condition presented. If you think it would be useful, I'll prepare a detailed review once finished and probably include some remedial tips. 

 

Given how long these have been marketed, someone else must have gone through this exercise previously? My searches only turned up some how-to blogs about disassembly and cleaning.  Helpful as they were, there should be more.


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#83 Masvingo

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Posted 02 January 2020 - 06:20 AM

Thanks for your initial comments. I look forward to hearing your further conclusions once you have had time to get to know the C90.



#84 quercuslobata

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Posted 10 January 2020 - 06:50 PM

Hi,

 

I just bought an old C90 on eBay. As you can see it the pictures it is a black tube "mirror lens" type with a serial number of 94572 and an optics number of 5202. Other than that I don't know anything about it.

 

I actually haven't even had a chance to use it yet as it didn't come with a diagonal or finder base. I just got a used hybrid diagonal that is long enough for the deeply recessed retaining screw, so I'm getting closer to it being useful. I got it as a grab and go for planets to complement my g and g short tube refractor.

 

There are no holes for mounting a finder base? Any suggestions about how to add one (drilling+tapping vs. epoxy vs.???).

 

Thanks.

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#85 Uranotopia

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Posted 11 January 2020 - 12:23 PM

Hi,

 

I just bought an old C90 on eBay. As you can see it the pictures it is a black tube "mirror lens" type with a serial number of 94572 and an optics number of 5202. Other than that I don't know anything about it.

 

I actually haven't even had a chance to use it yet as it didn't come with a diagonal or finder base. I just got a used hybrid diagonal that is long enough for the deeply recessed retaining screw, so I'm getting closer to it being useful. I got it as a grab and go for planets to complement my g and g short tube refractor.

 

There are no holes for mounting a finder base? Any suggestions about how to add one (drilling+tapping vs. epoxy vs.???).

 

Thanks.

What a pretty nice C90! Congrats !!!

I know some guys, who have taped a simple cheap dotfinder with tape on their scopes - not looking so well, but that seems to work and you have no need, to drill into your C90's tube. Or tape a telrad onto the tube.

Another possibility is to use the C90 on a double mount (f.i. the SkyTee).


Edited by Uranotopia, 11 January 2020 - 12:25 PM.


#86 cchaven

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Posted 12 January 2020 - 08:47 PM

I don't think I've ever put my orange C-90 here...it's a USA made orange tube C-90 telescope version, serial# 917577.  It has a LAR and the original Vixen finder scope on it.  I've used it for photography and it's currently mounted piggyback on my C-8.  It's my avatar and I've had it for about 6 years.


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#87 Masvingo

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Posted 18 January 2020 - 09:01 AM

Thanks, quercuslobata and cchaven for the C90 details.  I've updated the C90 Registry to Edition 5.1 and have also included a black spotter with screw-on dew shield that is on Ebay (UK) at the moment.

 

 


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#88 Uranotopia

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Posted 19 January 2020 - 11:33 AM

Great!!!

You are going to collect more and more data of vintage C90. IMO very important information to estimate the age of an older C90!  

Thx a lot for sharing these informations!


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#89 Augustus

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Posted 29 January 2020 - 06:37 PM

Just bought #95037


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#90 Utahn

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Posted 01 February 2020 - 12:58 AM

Earlier today I purchased a C90 with a 2.5x multiplier, an 18mm EP, a porro prism and a 90deg mirror. $200.

There is also a camera mount, but off hand I don't know what camera.

 

S/N 909164

Etched on the class of the front lens is 8317

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#91 Uranotopia

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Posted 01 February 2020 - 10:12 AM

Earlier today I purchased a C90 with a 2.5x multiplier, an 18mm EP, a porro prism and a 90deg mirror. $200.

There is also a camera mount, but off hand I don't know what camera.

 

S/N 909164

Etched on the class of the front lens is 8317

Looks very nice!
Will you have opportunity to observe with it soon?


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#92 Utahn

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Posted 03 February 2020 - 10:11 AM

Thankfully It was clear Saturday night. I was able to observe the moon. 

I purchased the attachment so I can mount it onto my C8.


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#93 Masvingo

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Posted 15 February 2020 - 01:05 PM

Thanks to Augustus and Utahn for the C90 details which I've added to the C90 Registry which is now at edition 5.2.

Augustus, what model is your C90 (telephoto, spotter or astro) and can you see a number on the front lens?  Any chance of a picture? 

 

Both, is the maker's mark on the finder an oval-M, circle-dash or circle-V?

 

I've also added the details a late model C90 with the ribbed rubber focusing ring that is currently on Ebay.

 

 


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#94 Augustus

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Posted 15 February 2020 - 01:11 PM

Thanks to Augustus and Utahn for the C90 details which I've added to the C90 Registry which is now at edition 5.2.

Augustus, what model is your C90 (telephoto, spotter or astro) and can you see a number on the front lens?  Any chance of a picture? 

 

Both, is the maker's mark on the finder an oval-M, circle-dash or circle-V?

 

I've also added the details a late model C90 with the ribbed rubber focusing ring that is currently on Ebay.

Astro. I sold it before I got a look at the front lens.

 

I believe it was Circle-V.


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#95 Masvingo

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Posted 15 February 2020 - 01:17 PM

Thanks Augustus, I've updated the registry.


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#96 houndsbourgh

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Posted 24 March 2020 - 11:48 AM

Originally an Astro this little guy came to me with some issues. Looks like the front glass had been loose for some time. Edge of the lense has a chip and several scars from rattling around in the OTA. Lucky for me the chip is not in the optical path. Scarring around the edge was minimized by a friend who restores antique cameras. The chip was filled and the edge blackened. Very hard to see any issues even under the harshest inspection. After a good cleaning and servicing optics are solid. Views are just as good as it's minty twin which resides on the drive now. Still finding a few missing bits with some members help. Great scope back in action.

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#97 Masvingo

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Posted 28 March 2020 - 11:32 AM

Many thanks, houndsbourgh, for the details of your 'new' C90 - its great to hear that you have brought it back into action.  Is there a maker's mark on the finder eyepiece, eg circle-V or circle-T?

 

I've added the details to the C90 Registry which is now at edition 5.3.

 

Please keep the contributions coming, everyone.

 

 



#98 houndsbourgh

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Posted 28 March 2020 - 12:26 PM

It is marked circle-V. My other C90 918503 is now the Astro. Circle-V finder as well.

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Edited by houndsbourgh, 28 March 2020 - 12:29 PM.

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#99 ANM

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Posted 29 March 2020 - 01:58 PM

Hi all!

I read somewhere that the C90 telephoto lenses are black and either 500mm or 1000mm focal length. Anyone know if this is correct?

 



#100 Masvingo

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Posted 29 March 2020 - 02:23 PM

It is marked circle-V. My other C90 918503 is now the Astro. Circle-V finder as well.

Thanks houndsbourgh, I've updated the entry for #919048.  I note your other C90 serial number is quite close, did you specifically look for one with a similar number or was it just chance?
 




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