Idiotic (I suspect) question

[brianb]

The standard Celestron 1.25" visual back has a male thread on the BACK end (the end you push the diagonal / camera / eyepiece into). It is obviously not a T thread, it's several millimetres less in diameter. And it's not to hold the diagonal or whatever since this is secured by a set screw.

What is the back end thread supposed to screw in to?

[Psychobilly]

Here you go Brian...

The standard visual back on my Schmidt-Cassegrain telescope (SCT) has threads on the outside of the barrel. What are these threads for?

The only idiotic question... is the one that doesn't get asked...

Peter...

[Earl]

My Meade has a Threaded visual back, and it allows me to connect a variable camera / eyepiece projection adaptor.

Ill take some photos as it will be better than my attempt with words

[michael.h.f.wilkinson]

The thread on the standard Celestron visual back is also for eyepiece projection attachment. It is actually a rather clumsy set up, which has lead to various outburst of rage, along the line of: "HOW THE HELL AM I SUPPOSED TO FIND THE blumming PLANET LIKE THIS!!!!!":BangHead:

1. You first find the planet and carefully centre it with the EP directly in the visual back (w/o diagonal, which can already be a pain).
   
2. You then VERY CAREFULLY thread the EP projection tube over the EP and onto the visual back.
   
3. Attach camera, and pray the object is in the field of view.
   
4. If not fiddle around until either: (a) you get it in the field of view, or ( you give up and goto 1.
   
5. Repeat until success or fit of rage
   

Much better to use a flip mirror (blood pressure during imaging session MUCH lower;))

[brianb]

Thanks guys ... I guessed it was something simple, and not of practical significance so far as I'm concerned, I was just curious.