Focus for film

As I poke around on the Web, I've only seen reference to Hartmann masks being used for focusing digital imaging. Can I use it effectively with my Nexstar 11 GPS and a 35mm film camera with a ground glass screen..? I've been dabbling for a while with both film and basic digital cameras for a while now, and if I spend another dime on anything astronomic, the family CFO will kill me. Making a Hartmann mask would be a nice super-cheapo option! I'll make one anyway and see, but if there are any wise old salts out there with some advice, I'm all ears..
Thanks!
JR

Yes, they work. No, they are not perfect. But close to 95 per cent perfect (I have no idea where that number comes from besides my imagination!)--and that is pretty cost effective. They can get you close enought that other problems, like seeing, bad tracking, and such probably count as much as focus.

Alex

Jay,
You may also check out this site on home-made knife edge focusers.

http://www.astropix.com/HTML/I_ASTROP/I08/I0815/I0815.HTM
( Click the foward and backward arrows of this link for various focusing methods )

I purchased a junk matching camera body from a local camera shop for $10, tore out the shutter and cut a hole in the back and glued on an old .965 diagonal, and now have a poor mans stiletto focuser.

Bob