Re: [APML] Proper Use of Varimagni Finder

["Joseph O'Neil" <joneil@multiboard.com>]

>I'd appreciate any advice for using the Varimagni to focus the lens. I've
>practiced with it during the day on terrestrial objects, but focusing on
>stars is completely different, as we all know. BTW, I have a Beattie screen
>in the camera. Do I just focus with the Varimagni at its highest
>magnification setting (2.5x) until the stars look the sharpest, or is there
>more to it than that? Normally I photograph one f/stop higher than the
>lens's wide open setting.

-snip-

         I would hazard to guess the problem is yoru Beattie screen, not 
the Varimagni, whihc I have used myself.  Any screen that that "intesifies" 
or "concentrates" light I find is poor for focusing not only on the stars, 
but even in low light situations.
         I forget the part/model number, but what you want to use is a 
plain screen, as plain as possbile, that will focus nicely on your 
Varimagni finder, not just for astro-photo work, but even terrretial macro 
work.
         Also, some 50mm lenses are asbolute dogs, and it's hard to say 
what they are until you use them.  Focus wide open, and then stop down two 
stops - say to F4 for example.
         as for your telephoto, if all else fails, focus as sharp as you 
can on the moon's terminator some night, mark the spot on your lens with 
tape, and then next moonless night, try that focus setting as a starting 
point.  Assuming the ambient temperature is about the same as the night 
when you set the moon's focus, it should be close.
         Try focusing then ont eh stars, and when you come to what you 
think is close, look at yoru tape mark.  for an experiemnt, shoot two 
shots, one  at yoru "moon" mark, the other at yoru star mark,a nd see 
which, if either, comes closest.
joe



http://www.oneilphoto.on.ca
http://www.multiboard.com/~joneil
"Una salus victus nullam sperare salutem"


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