Anyone Here Use a Hartmann Mask?

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

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usenet *at* davidillig dawt com