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1970s Orange Celestron C8

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#1 Cosmic_Lox

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Posted 28 July 2020 - 05:19 PM

Just bought an early-mid 1970s classic orange c8. The two motors turn on and spin, tracking seems to work (although I haven't tested it out yet beyond turning it on and seeing them spin). 

 

I have a 1.25"/2" (works with both focusers) T adapter that I've used with my Nikon d3100 and 6" dobsonian and Meade etx 70, both without a problem. But it's slightly too small for the C8 (when using the 2" adaptor), does anyone know why? 

 

The guy I bought it from had a diagonal with a 2" eyepiece when I tested it, and it looked just like a modern eyepiece without an adapter, so I assumed my t adaptor would fit. It does not.

 

Does this mean modern 2" eyepieces or a diagonal won't fit as well? Which t adapter must I use if not a (normal) modern 2" adapter? 

 

Thank you in advance to anyone who can help. 

 

 

-Eric

 

IMG_7357 copy.jpg


Edited by Cosmic_Lox, 28 July 2020 - 05:22 PM.

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#2 B 26354

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Posted 28 July 2020 - 05:29 PM

The standard visual-back on these older C8s was a 1.25" one. Has yours been replaced with a 2" visual back?


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#3 ANM

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Posted 28 July 2020 - 05:52 PM

does it thread on the SCT threads? maybe just a turn of so?



#4 CHASLX200

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Posted 28 July 2020 - 06:04 PM

Looks to be a 1977 or later made C8.  The holes in the forks switched to no holes in 1976.



#5 ANM

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Posted 28 July 2020 - 06:16 PM

Are you talking about where the visual back threads on? 



#6 Don W

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Posted 28 July 2020 - 06:50 PM

Tripod is much newer. Not sure about the wedge.


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#7 Beeham

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Posted 28 July 2020 - 08:47 PM

Yours looks just like mine, which is a 1977.  Mine originally had the factory 1.25" diagonal, I replaced it with a contemporary 2" diagonal with ordinary SCT threads.  I have used 2" eyepieces with no problem.

 

If memory serves the SCT threads on the cell are 2" x 24 tpi.

 

I hope this helps.  Cheers!



#8 Cosmic_Lox

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Posted 29 July 2020 - 04:15 PM

@B 26354: I think I have discovered the problem: This telescope came with no visual back. The diagonal being used when I tested the telescope must have been a threaded type (I was unaware of this option as I'm new to SCTs) and in all of my excitement I just didn't notice. 

 

The diameter of the opening on the back of the C8 is 2" and I thought that was the visual back, hence my incorrect assumption. 

 

 

@ANM: You are spot on. I was (unknowingly) referring to where the visual back screws on and not the visual back itself. I have purchased a Celestron-made t adapter which screws directly onto the back of the SCT. I am in the market for either a 2" visual back with a 2" diagonal and 1.25" adapter, or simply an SCT (threaded) 2" diagonal with an adapter. (Also in the market for my first 2" eyepiece. All I have are the cheapo 1.25" eyepieces that came with novice-telescopes.) I will make an add in the classifieds section here today. 

 

@CHASLX200 and @Don W: I agree. Seems like somewhere between '77 and '79. I'm still getting mixed info regarding the tripod and mount (both of which are celestron branded). 

 

@Beeham: Does yours have the same tripod and mount/wedge? (The black solid-legged one as opposed to the silver triangular-legged tripod.) I'm most likely going to get a contemporary (elegantly put!) 2" diagonal as well. Will make the ad today. In the market for my first 2" eyepiece too.

 

 

Your information helped me greatly. Thank you all very much! 

 

-Eric 



#9 Don W

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Posted 29 July 2020 - 05:24 PM

My info on the tripod is not mixed. That tripod is not from the same era as that telescope. That style of wedge was used for many years. It could be original or it could be from a decade later.

 

Here is the proper tripod from that era. It's referred to as the Locked Triangle Tripod.

 

locked triangle tripod (2) (Medium).jpg

 

 


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#10 Cosmic_Lox

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Posted 29 July 2020 - 05:50 PM

@Don W: Thank you for this info! It does make sense that the original tripod was swapped out for whatever reason, just wasn't sure. 



#11 CHASLX200

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Posted 29 July 2020 - 05:58 PM

My info on the tripod is not mixed. That tripod is not from the same era as that telescope. That style of wedge was used for many years. It could be original or it could be from a decade later.

 

Here is the proper tripod from that era. It's referred to as the Locked Triangle Tripod.

 

attachicon.giflocked triangle tripod (2) (Medium).jpg

His tripod looks to be a 1983 or later tripod. They were known to have leg locks that broke. I had one and loved it.


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#12 Cosmic_Lox

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Posted 29 July 2020 - 06:44 PM

@CHASLX200: I assume you're referring to Don's tripod, but I want to make sure, are you? 

 

...Because my tripod has one broken leg lock but I was under the impression that mine was from the 1980's and Don's was from the 1970's. Do you disagree with this assessment? 


Edited by Cosmic_Lox, 29 July 2020 - 06:46 PM.


#13 CHASLX200

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Posted 29 July 2020 - 06:55 PM

@CHASLX200: I assume you're referring to Don's tripod, but I want to make sure, are you? 

 

...Because my tripod has one broken leg lock but I was under the impression that mine was from the 1980's and Don's was from the 1970's. Do you disagree with this assessment? 

I was saying your tripod is from around 1983- 85.



#14 Cosmic_Lox

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Posted 29 July 2020 - 06:59 PM

@CHASLX200: Ah, it is all starting to come together now, hah. I really appreciate all of the help and information from you guys. This is pretty amazing. 



#15 RichA

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Posted 29 July 2020 - 07:23 PM

His tripod looks to be a 1983 or later tripod. They were known to have leg locks that broke. I had one and loved it.

I've seen the top part of the tripod break (similar designed) when the leg-spacer that was screw upward was screwed too tight.  Luckily, this tripod doesn't have that triangular spacer and has struts at the bottom of the legs.



#16 B 26354

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Posted 29 July 2020 - 08:12 PM

@B 26354: I think I have discovered the problem: This telescope came with no visual back. The diagonal being used when I tested the telescope must have been a threaded type (I was unaware of this option as I'm new to SCTs) and in all of my excitement I just didn't notice. 

 

The diameter of the opening on the back of the C8 is 2" and I thought that was the visual back, hence my incorrect assumption.

 

No problem. Easy to understandgrin.gif

 

 

@ANM: I have purchased a Celestron-made t adapter which screws directly onto the back of the SCT. I am in the market for either a 2" visual back with a 2" diagonal and 1.25" adapter, or simply an SCT (threaded) 2" diagonal with an adapter.

Good luck. I bought my C8 new in '77. In April of this year, I began looking into putting a 2-inch visual back on it, so that I could use my two 2" eyepieces. Unfortunately -- at least as far as I was able to determine -- none of the currently-made C8 2-inch visual backs have threads that match the threads on my C8, because the pitch of those threads was changed, sometime in the early '80s.

 

Here's my C-N thread, with the solution that I ended up using:

 

https://www.cloudyni...-for-a-1977-c8/

 

I'd be very curious to learn whether or not the T-adapter which you purchased, really does screw onto this older C8 of yours.

 

Yours looks just like mine, which is a 1977.  Mine originally had the factory 1.25" diagonal, I replaced it with a contemporary 2" diagonal with ordinary SCT threads.  I have used 2" eyepieces with no problem.

Exactly which diagonal is this? Could you possibly provide a link?



#17 Cosmic_Lox

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Posted 30 July 2020 - 02:40 PM

@B 26354: Great literature! Definitely led me down the rabbit hole lol.gif . I like how someone summed up this query: "They fit and they don't fit."

 

My t adaptor and diagonal (both coming in the mail now) have the wider-spaced-tooth fasteners. I don't know if that really means anything or not, but there might be a correlation between the space of the teeth on the faster and the ever-so-subtle difference in thread size. I'm pretty sure they are also both older pieces. In any case, I will post here whether they end up fitting. 

 

There was a diagonal on this telescope a few days ago when I tested it (which did not come with the scope) and the guy I bought it from encouraged me to buy a diagonal without mentioning any oddities or particulars about fit. He's a nice and knowledgeable guy, so it leads me to believe that he was unaware of this issue. Either this particular telescope will allow modern diagonals to thread on, or (more likely) the guy I got it from had an older diagonal and just didn't realize he got lucky with fit. 

 

We shall see. 


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#18 Cosmic_Lox

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Posted 01 August 2020 - 01:35 PM

UPDATE:

 

The T adaptor came and it's too small. Only threads on about 1.25 rotations, just as everyone else has explained.

 

It did thread on enough to attach my camera without falling off and achieve prime focus, which was pretty fun. Even with this half-on t adaptor I was able to see Jupiter and its jovian moons, Saturn (albeit no ring detail or definition, but an oblong shape to silhouette, if you will, the rings), and a nice close up of the moon.

 

Next step is to try the diagonal which is coming today. If that doesn't thread on properly either, then I'll do the grinding/lubrication process which I am utterly unfamiliar with. However, from what I've read, I am willing to take on the challenge.

 

Clear skies.



#19 Cosmic_Lox

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Posted 01 August 2020 - 01:53 PM

Also, just wanted to mention, I wanted to post a picture of the serial number on my OTA, but it appears to literally be scratched off. 
 
 image1.jpeg
 
Weird, huh? Some rebel amateur astronomers stealing telescopes and trying to cover their tracks? lol.gif
 
Oh, and when messing with the wedge, trying to adjust the angle of the mount, the plastic 'wings' on the screws broke off. All of them. My needle nose pliers are not doing the job. I don't have many tools, any suggestions? Obviously, I'll try a standard adjustable wrench, but I doubt it will properly grip.

 

image1 2.jpeg

 

 

Thank to anyone who can help,

Eric



#20 CHASLX200

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Posted 01 August 2020 - 02:51 PM

I would use vise grips and just replace them all.


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#21 Cosmic_Lox

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Posted 01 August 2020 - 03:05 PM

I'll do that. Thank you! 



#22 CHASLX200

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Posted 01 August 2020 - 03:14 PM

Plastic dries out after so many years.



#23 Don W

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Posted 01 August 2020 - 05:11 PM

You can replace them with hand knobs.


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#24 CHASLX200

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Posted 01 August 2020 - 06:03 PM

You can replace them with hand knobs.

That would be the best way to go. Just after 30+ years the old plastic hand knobs can break easy as most all plastic does not age well.



#25 davidmcgo

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Posted 01 August 2020 - 08:57 PM

I prefer to just use socket head screws and keep a set of Allen wrenches at hand.  Easier to get the extra torque to keep the wedge from slipping that way.

 

Dave


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