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Selsi 80mm refractor question (rear adapter missing)

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#1 overland

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Posted 11 January 2021 - 04:41 PM

I bought a Selsi 80mm refractor over the weekend. It's complete, I think, except for one thing: there's no adapter at the rear of the OTA to accept a diagonal.  It looks like it needs something 1.5" in diameter with male threads. Any suggestions on what I might use that would work?


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#2 Don W

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Posted 11 January 2021 - 05:37 PM

Normally those scopes came with a tailpiece that accepted .965" eyepieces and diagonals. Not sure where to find an original. That said, you can get a tailpiece that accepts 1.25" eyepieces and diagonals.

 

https://optcorp.com/...yepiece-adapter



#3 Van Do9:3

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Posted 11 January 2021 - 05:47 PM

Congrats on acquiring a very nice classic. Pictures would be greatly appreciated and helps us better understand the issues. 



#4 photoracer18

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Posted 11 January 2021 - 05:48 PM

Normally those scopes came with a tailpiece that accepted .965" eyepieces and diagonals. Not sure where to find an original. That said, you can get a tailpiece that accepts 1.25" eyepieces and diagonals.

 

https://optcorp.com/...yepiece-adapter

That will only work in a Vixen not a Selsi.


Edited by photoracer18, 11 January 2021 - 05:51 PM.


#5 overland

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Posted 11 January 2021 - 06:16 PM

I'm sorry,  but I can't figure out how to upload photos.



#6 overland

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Posted 11 January 2021 - 07:02 PM

Here it is. It measures about 36mm, inside diameter:

 

 

Selsi ota (2).jpg


Edited by overland, 11 January 2021 - 07:05 PM.


#7 scopeboy42

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Posted 11 January 2021 - 07:09 PM

From your photo it looks like the black adapter screws on the drawtube - I can see the threads. Take this off and see if the drawtube inside dimension is closer to 36.4mm.



#8 overland

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Posted 11 January 2021 - 07:26 PM

You're right: there's some kind of adapter in there. Without the adapter the ID of the drawtube is about 42mm. The inside of the adapter is about 36mm. The OTA, of course, is Japanese.



#9 Don W

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Posted 11 January 2021 - 08:09 PM

That will only work in a Vixen not a Selsi.

Well then you can tell my Selsi that it doesn't work then.

 

Vixen adapter.jpg

 

 

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#10 scopeboy42

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Posted 11 January 2021 - 08:27 PM

I would give the Vixen #3720 a try as mentioned above - it may fit in your black adapter. OPT is listing it 14-28 days out but Vixen Optics has 11 of them in stock.

 

https://www.vixenopt...20.htm?CartID=1

 

People tend to hold on to them so they do not show up used very often. If it doesn't fit it will sell fast here on CN.



#11 Macguyver909

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Posted 11 January 2021 - 08:40 PM

I bought one of these, works great. $25.00 it is a vixen 3720 as mentioned above.

 

https://www.bhphotov..._to_31_7mm.html



#12 Garyth64

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Posted 11 January 2021 - 08:44 PM

This photo shows the difference between a .965" VB on the left, that would be found on a Sears 6339a, a Tasco 10TE-5, Tasco 7TE-5, et al,

to a 1-1/4" VB on the right with 36mm threads.  These two VBs do not have the same thread.

 

965 and 125 visual backs.jpg

 

This next photo shows the .965" VB on the left, that would be found on a Tasco 10TE, Tasco 7TE, 7TE-2, Shrine Manon, ATCO 1254, etal. 

That VB has 36mm threads and can be replaced with a 1-1/4" VB on the right with 36mm threads.

 

same  threads VB.jpg

 

(I had to edit this post to correct a mistake.)


Edited by Garyth64, 12 January 2021 - 10:08 AM.

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#13 overland

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Posted 12 January 2021 - 08:53 AM

Thanks, everybody, for the quick and useful advice.



#14 Van Do9:3

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Posted 12 January 2021 - 02:12 PM

Here it is. It measures about 36mm, inside diameter:

 

 

attachicon.gifSelsi ota (2).jpg

What is the adapter in this photo used for? What are the thread sizes? 
 

Thank you. 



#15 Don W

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Posted 12 January 2021 - 02:51 PM

It may be an adapter for a T-thread camera mount. Not sure of the thread size.



#16 Kasmos

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Posted 12 January 2021 - 03:22 PM

Here it is. It measures about 36mm, inside diameter:

 

 

attachicon.gifSelsi ota (2).jpg

Looking at your photo, the focuser and knobs look like a APL-Vixen model 247, so a Vixen Visual Back will work.

BTW, Check the bottom of the focuser as some have Vixen embossed on them.

 

They vary in design by year but this looks like your scope. Go to post #22 to see how the VB fits into the ring on your rack tube. 

 

https://www.cloudyni...-for-a-new-guy/

 

Your model should have the Polaris Mount


Edited by Kasmos, 12 January 2021 - 03:23 PM.


#17 overland

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Posted 14 January 2021 - 12:54 PM

A new problem  has come up. I noticed a crack in the metal (aluminum?) housing at the end that holds the objective lens. The lens itself is fine, and there's no displacement of the housing, but the crack is there. Should I try to put something over it, like epoxy, to prevent it from moving in any way? Or just live with it? There's another metal piece at the end that screws into this housing, perhaps to hold the lens in. It's also the part that holds the collimating screws. That's not cracked.

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Edited by overland, 14 January 2021 - 12:56 PM.



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