What's the Process for EP and FL testing

[glend (Glen)]

Just wanted some suggestions for the best way to determine the exact place to locate the focuser (and backplate) on a refractor build. I was going to use the "scope on a stick" technique to map the various EP focal points by moving the focuser in and out to assess the range needed. The focuser is a Moonlight with 4.5" of travel, so I think I have enough range there. I have some Andrews Binoviewers which I know will need some extra intravel. I have heard that I should start with a 2" 30-40mm EP because of the stop size and work down from there. Is is better to start with the binos and mark that as the furtherist IN and then work out from there by focal length of the EP or stop size?

[astro744]

Don't forget the length of light path taken up by the diagonal, say 120mm. (Measure it to be exact).

A typical Binoviewer is 120-130mm so if you want to use a binoviewer (without 2x amplification) you will need to shorthen the tube by 120-130mm or use it in straight through mode.

Binoviewers in 1x mode are only good for SCT's where focus is achieved by moving the primary mirror or shortened refractors when using a diagonal.

[glend (Glen)]

Originally Posted by astro744

Don't forget the length of light path taken up by the diagonal, say 120mm. (Measure it to be exact).

A typical Binoviewer is 120-130mm so if you want to use a binoviewer (without 2x amplification) you will need to shorthen the tube by 120-130mm or use it in straight through mode.

Binoviewers in 1x mode are only good for SCT's where focus is achieved by moving the primary mirror or shortened refractors when using a diagonal.

And if I want to use the binos with the 2x barlow?

[astro744]

Originally Posted by glend

And if I want to use the binos with the 2x barlow?

I'm only familiar with the Tele Vue Bino Vue. If I use the 2x amplifier/corrector nosepiece I can get focus in a my ED80 refractor with 2" diagonal. I cannot with the 1x nosepiece unless I use it on my C9.25.

I'm not sure if using a standard Barlow either before or after the diagonal will allow you to reach focus with the binoviewer you have. Perhaps others can respond here.

[MattT]

Originally Posted by glend

And if I want to use the binos with the 2x barlow?

You'll have to rack the focuser further out. That is what I do with my WO's which are the same I believe as yours. With the long drawtube on the Moonlite should be no problem reaching focus.