Expert: Paul Wagner - 2/12/2006

Question
i have a 10" newtonian scope, but it is really big- about 5 feet long.  it is a hassle to set up and put on the big tripod.   is there a way to convert it to a kind of schmidt cassdegrain scope.  I don't want to cut a hole in the 10 inch mirror, but maybe there is a way to cut the tube a little longer than half, put a 5" diameter mirror in front, and move the 45 deg elliptical mirror and the eyepiece to the back.
then i would just keep it on the tripod and move the whole thing out when i want to view.  is there a kit for this?  any ideas?  

Answer
Dear Mike:

There are a million different ways to adapt telescopes...but they all start with the optics themselves.  Yes, you could do what you are suggesting, but the light loss and diffraction distortion from that large secondary mirror would really affect your scope's performance.  Nor is there a kit for this kind of thing.  

You might have some fun looking up the optical designs in Amateur Telescope Making, edited by Ingalls. It's a three volume set with every possible combination of mirrors and lenses.  But I don't think any of them will solve your problem.

I think you have three possible solutions:

1.  Sell you scope and buy one that is more suited to your uses--maybe a real SCT.

2.  Adapt your scope to a dobson mount--this won't track celestial motion, but it will be a lot lighter and easier to move, set up, and carry around.

3.  Sell the primary mirror and buy one with a much shorter focal length---and then adapt the tube to match.

If it were me, I would vote for #2--but then I have two big scopes, both dobson mounts, of 13 and 17 inches.  And I can pick up either scope by myself.

Paul Wagner