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Visual back threads - Why?

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#1 iverp

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Posted 10 April 2013 - 08:01 AM

I have been had a Meade SCT for several years now, but have never figured out why the standard SCT visual back is threaded on eyepiece end. Obviously the collar that attaches it to the SCT port is threaded, but what fits the other threads? I'm attaching a small pic with the threads I mean arrowed, just so everyone understands the ones I'm referring to.

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#2 orion61

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Posted 10 April 2013 - 09:15 AM

I believe there used to be an F5 Focal reducer that screwed onto it so no loss of the light cone..
Also certain camera equipment will screw onto it..
mainly for photography.
I have/had a really old Accy catalog that showed some of these accys. Then Celestron came out with the GREAT Japanese made F6.3 FR/FF.. Still the best.. I have had them all.
If you are in the market for one try to get the MIJ one.
I find the Stellar images to be more pleasing, color and
sharpness.

#3 Brian Risley

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Posted 11 April 2013 - 05:07 PM

Tele-extender threaded on (about 6" long). Allowed an eyepiece to be placed in the holder (provided it wasn't to large, the old ones weren't) and then a camera T-ring went on the end.
This was the old standard for film planetary and lunar photography.
Brian

#4 Christopher Erickson

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Posted 12 April 2013 - 12:27 AM

I have been had a Meade SCT for several years now, but have never figured out why the standard SCT visual back is threaded on eyepiece end. Obviously the collar that attaches it to the SCT port is threaded, but what fits the other threads? I'm attaching a small pic with the threads I mean arrowed, just so everyone understands the ones I'm referring to.


Those are standard T-threads.

http://en.wikipedia.org/wiki/T-mount

Very common with telescopes and camera adapters.

#5 Matthew Ota

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Posted 13 April 2013 - 03:52 PM

That thread where the arrow is pointed is also used for Meade's older 2 inch star diagonal, which screwed onto the adapter.

#6 Hamsterdam

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Posted 19 April 2013 - 04:08 PM

Yes, My LX200 10" f/6 has a diagonal with a collar-type nut that screws onto the visual back of my scope. It has been awhile, so I do not recall if my JMI focuser attaches the same way. I do know that before I was aware a field flattener was of no use with my f/6, the threads on it do not match the visual back. It is almost like Standard vs SAE, in the bolt world. Anybody looking for a Meade f/6.3 flattener?






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