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 -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.