Re: Calculating Magnification on a Telescope + Camera setup

In order to figure out your focal lenght you need to first know the magnification of the telescope being used. (Focal Length of Telescope divided by Focal length of eyepiece I.E. 1000mm/20mm - 50X as in your example) Knowing that, you then can multiply the focal length of the lens being used by the magnification (Camera Zoom lens at 8mm X 50 = 400mm) If you need to find the 35mm equivalent then you need to know the relationship between your sensors physical size compared to a 35mm frame. The camera manual should have this information. (I.E. and Olympus E-500 has a 150mm lens that is the equivalent of a 300mm lens in 35mm therefore 300/150 = 2. Now you can multiply your focal length by this factor to arrive at the 35mm equivalent. So in our above example we have 400mm x 2 = 800mm equivalent in 35mm)


I'd worry more about understanding the exposure values rather than the magnification equivalents if I was looking to do any serious astrophotography. It's much easier since the days of Hypered film and 3 hour guided exposures. You can dial in 3200ISO and make excellent exposures in a fraction of the time it used to take with none of the mess and bother either!