Binoviewers, magnification and focal length

[Bender]

Hi,

While I was looking around for eyepieces I came across binoviewers. Love the idea but got a bit confused.

First the focal length. I my scope has 770mm and the binoviewer has a optical length of 110mm plus another 30mm that the 2" diagonal ads to the light path. Thus this mean I have to calculate with 900mm when computing the magnification a certain ep produces ?

Second, with a 1.7x glass path corrector that should reduce the backfocus required. Does this multiplies the magnification by 1.7 ? e.g. for a 9mm ep (900mm/9mm)x1.7

And third, specifically for my scope. The 1.7x glas path corrector leaves 60mm backfocus required for the binoviewer.

My scope needs a 60mm extension tube to come visually into focus. Can I just leave the extension tube out and both 60mm's will cancel each other out?

Apologies if this is all blatantly obvious

[Peter Drew]

Hello Bender. Adding components to your tescope doesn't add to its nominal focal length. The 1.7x component however will increse the basic magnification by at least this amount. You might well be able to dispense with the 60mm spacer when usinng this item. Stick with it, binoviewing on lunar and planetary observation is awesome.