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DSLR at prime focus

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DSLR at prime focus

I'm a visual observer with a moderate amount of experience and a couple of DSLRs on my hands.  I've been slightly interested in photometry for some time, but not enough to spend a wad of money on a decent CCD imaging system.  I've noticed the Citizen Sky DSLR project, and perused the pages of the tutorial, but it seems to me that the approach there is not really what I want.  Unlike the target audience, I have a relatively fast (f/6) telescope available (a Maksutov-Newtonian), with a decent (Losmandy Gemini) mount.  So the natural thing for me is to spend $70 for an adapter that will allow me to put the focal plane of a DSLR at prime focus.

It seems pretty clear that a) I don't need to do darks, because both of my cameras have automatic noise reduction features, and that b) given that the field of view (even with my full frame sensor) will be less than 2 degrees in its diagonal dimension that I don't have to worry about differences in atmospheric mass across the field (this is especially true because my "horizon" is at an elevation angle of over 15 degrees).  My first question concerns the procedure for doing flats.  Do I just aim my scope at a unifomly illuminated target (like a piece of foam core board)?  Second, should I deliberately defocus, given that the pixels will intercept about one arc second and thus will be modestly overfilled even in perfect focus?

I'd like to hear from anyone out there who's done what I want to do.



LaurenRosenbaum's picture
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