[AZ-Observing] Re: DLSR Focusing

  • From: Rick Scott <rmscott@xxxxxxx>
  • To: az-observing@xxxxxxxxxxxxx
  • Date: Wed, 04 Jul 2007 23:43:45 -0700

I use the Canon Right Angle Finder C along with an occulting bar that I 
hold in front of the telescope to act as a rough Hartman mask. The 
occulting bar can be anything, even your arm, if it's wide enough 
compared to the aperture to block a significant portion of  the light 
path. The bar is positioned to pass through the center of the aperture 
leaving a light path on either side of it. By doing this you'll see a 
double image when the focus is not correct. Just focus until the 
doubling disappears.

Rick Scott



Jimmy Ray wrote on 7/4/2007 11:38 AM:

I'm looking for the group's opinion on DLSR focusing when taking 
astrophotos. I find that when I have the camara body mounted in prime focus 
(Canon XTi to a 8" or 11" SCT) it is dificult to assess focus and to date 
the results haven't been "stellar". I was looking at the Canon magifying 
angle finder "C" which has 1.25x and 2.5x and runs about $180 delivered. 
Other options or tricks?

Jimmy Ray




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