I use a variant of a Hartmann mask with my 10" LX200 for imaging, but it's
just as useful with a film camera. The one I use has triangle openings
instead of round. When all is perfectly in focus you see a clear triangle
in the eyepiece which can appear upright or reversed. This will tell you
whether you are inside or outside of focus.

Al


"Davoud" wrote in message
...
If so, I would be pleased to hear of your experience.

I plan to try one for focusing with an SLR (film or digital) at prime
focus on an 8" SCT.

Tell me where to stick it -- must it be placed immediately in front of
the corrector plate, or can it be placed over the end of the dew
shield?

TIA!

Davoud

--
usenet *at* davidillig dawt com