Is it possible to modify this refractor?

[StutzJr]

So I have this old soviet made Typnct-3 20x50 refractor (http://www.google.com/search?q=typnct+3+20x50+telescope&tbm=isch&tbo=u&source=univ&sa=X&ei=5-KhUbTZMuOyiAe9oICYDw&ved=0CFIQsAQ&biw=1280&bih=820#tbm=isch&sa=1&q=typnct-3+20x50&oq=typnct-3+20x50&gs_l=img.3..0i24.5043.5043.2.5269.1 .1.0.0.0.0.195.195.0j1.1.0...0.0... 1c.1.14.img.LiEtyqXNUL8&bav=on.2,or.r_qf.&bvm=bv.47008514,d.dGI&fp=3145cc035a297ee&biw=1280&bih=820) scope that my dad gave me a long time ago. Now that I have been using a 6" dob for a few months I am wondering whether I could put the old refractor to some better use. I never really got much out of it when I was younger because I didn't have a decent tripod, and because it is a straight through spotting scope - it is not convenient to look through when pointing up at the sky.
Having said that, it is a good scope with good optics and always gives reliable sharp correct image views.
This reference (http://www.binojapan.com/image/tourist3E.pdf) shows a rough blueprint of the internal optics.
What I would like to know is if there is any chance of retro fitting this scope either with a diagonal for more convenient viewing, or a makeshift webcam adapter on the back so that I could practise tracking perhaps with a mini eq mount?
Failing that, can anyone suggest how I might better utilise this scope for astro viewing on the occasions I don't have my dob in the car?

[bojan]

I used to have this one.. and still have its smaller brother (8x30).
After getting rid of terrestrial eyepiece, this achromat lens could be excellent for finder or guide scope.

Note, the focus is just in front of the first lens of the terrestrial eyepiece group (marked as 7), so this is where the camera sensor should be.

This terrestrial eyepiece is a good microscope (~10x), btw.

You just have to find some tubing (plastic) to make adapter to new wider angle eyepiece or guide camera.
Someone with lathe could be of a great help here, but fine and precision machining is not really necessary for this kind of modification.

[Terry B]

Don't know anything about the scope but I like the name of the lens cap on the schematic drawing "food cover" :D

[astronobob]

I seen Venus for 1st time through a similar scope back in the 80's : )
Looking at the blueprint, I think the main objective lens would be quite a fast F/Ratio, maybe F/5 or F/6'ish, similar to 8x50 Bino's !
If I was to madify this scope :P it could make a good finder, low power visual scope, Guide scope or with the webcam for live views of the moon or sun (only with proper solar filters) tho for the sun !

With the mock up attached : I would try seperate the Red circled halve and work with just the Blue lined section _ With just the blue lined section, i would think the Focus point/plain would be somewhere between the green lines ? ?

Id also be careful in doing this, marking peices etc so if not work, there be references to put back together correctly !

Not sure if matching your question or idea tho : ) :thumbsup:

[StutzJr]

Thanks for the suggestions! It sounds like some fairly major work to get anything to the focal point of the primary lens, more than I'm willing to do anyway. I just wondered if it would be a matter of removing the existing eyepiece (15) on the back and affixing a diagonal there.
Are there any issues with simply mounting a webcam in the exit pupil of the existing eyepiece?

[astronobob]

Ok, I assume the no 15 eyepiece unscrews out ? Then its a matter of addapting the diagonal. The tube which the eyepiece fits, looks quite narrow ? doy you have a measurment of this diameter ? Astro diagonals come in a small size of 0.96 of an inch which could be the closest by the looks, then possibly obtain a sleeve of soughts to marry the diagonal into or over the tube if it does not fit neatly? ?
The focusing is of just a slide in & out, as with all focusing designs, the travell is always restricted, so, there is always the question on enough travel to possible still reach focus after the inclusion of a diagonal, as a diagonal will alter (add 30-50mm) the distance of where the eyepiece is designed to sit in retrospect to the focal point/plain !

When the scope (as is) is in focus, how much travell can the focus tube slide further out ? if this is only 20mm, then may need to cut down this tube, but then, im getting a bit rough again hey :thumbsup:

Can only try and see ?