Olaf,
so a long post require a good answer, but I'm at work so I don't have
access to my bible of astronomical photography.
Anyway, I remember something.
First, how will wide on the film the image of an object:
D=(Fxd)/206265 where D=size on film (mm), F=focal of telescope (mm), d=size
of object in arcsec
Mars has a size less that 30" (if I remember correct) so with your 2800mm
telescope mars will be probably less than 0.4 mm on the film... too less
for viewing something (polar areas, color differences in different areas
etc). You should be able to have a good photo with a size of at least 1mm,
so you will need a focal of more than 7/8 metres!
The best method for taking a planet photo is to use a method called
"eyepiece projection" with a telescope but this is long story (briefly, a
telescope, an eyepiece as a magnifier and the camera).
Second problem is the movement of mars in the sky: depending on the
coordinate of mars it can move up to 15 arcsec in a second, a distance
comparable on the diameter of mars itself! So you will need not only a very
robust tripod, but an equatorial mount with a motor in order to have mars
not moving during the photo.
OM content: I suspect that the prefire method is well indicated with so a
long focal.
Ahh, what a long reply with my poor english, now is time for lunch...
Ralf Loi
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