Re: [APML] 35mm focusing - using a ronchi grating in filter holder?

[Jerry Lodriguss <jerry@astropix.com>]

This won't work.

The Ronchi screen has to be at the focal plane which is where the film is 
supposed to be.

Jerry




At 04:02 PM 7/20/2003 -0700, you wrote:
>I was looking at the van slyke page today, and came
>across this little nifty "filter slot adaptor".
>
>Its threads to a visual back and allows one to "drop"
>filters in the light path.
>
>And its inexpensive (for asto stuff).
>
>I got to thinking that one could drop in a ronchi grating and
>use it to find the focus with a film camera.
>(sorta like a stilleto.)
>
>Since the ronchi will be projected on the ground glass
>it might be acceptable on bright stars, etc.
>I would need to assume that the film plane and the
>ground glass are at the same distance from the
>T adapter (which should be and could be verified seperately.)
>If not then a stilleto makes more sense.
>
>Would this work?
>
>jeff
>
>
>
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