Telephoto to eyepiece adapter?

[GTom]

Recently got a 2.8/300  telephoto, which brings quite a serious aperture. Is there a convenient way to adapt a 2" eyepiece on the camera end for the occasional visual observations?

[Bivanus]

'Convenient' may vary  in meaning...Straight eyeball to something to telephoto ummm not really. Eyeball to Laptop screen to astrocamera to astrocamera/telephoto adapter much more likelly.

Omegon T2 adapter for Canon EOS lenses (can be found for other manufacturers too, I use Canon lenses)

 

[Bivanus]

On the other hand tho , dare and you shall (maybe) win ? 

Conversion of a 400 mm f5.6 old camera lens into a 70 mm f5.6 telescope - ATM, Optics and DIY Forum - Cloudy Nights

 

[GTom]

That one looks great, many thx! I'll check if I have enough backfocus, as I read it he removed part of the lens mount, that won't be possible with mine.

As for adding a camera and watching the shop on screen: i don't need any astrocam + laptop for that, I have my nikon z6 camera that I can attach anytime. Real, non-electronic view is what I am interested in.

8 hours ago, Bivanus said:

On the other hand tho , dare and you shall (maybe) win ? 

Conversion of a 400 mm f5.6 old camera lens into a 70 mm f5.6 telescope - ATM, Optics and DIY Forum - Cloudy Nights

 

[Louis D]

I MacGyvered together an adapter using a macro extension tube, a short length of PVC tubing, and 6 thumbscrews.  Three screws to hold the PVC pipe to the rear of the extension tube and three to hold and center the eyepiece.  It worked reasonably well as a spotting scope.

There's generally not enough back focus to use a diagonal, so straight through is your only option short of creating a relay lens or removing the back part of the lens.