Originally posted by XLXW Eric:
Excellent capture of the nebula. I am in the process of acquiring an old 1978 Celestron 5 inch Schmidt Cassegrain telephoto lens; and, I am going to learn how to do some astrophotography. I should get it hopefully sometime next week. The lens will be 1,250 mm in focal length Here is a total "novice" question: On the K3 camera or the K5 camera in the camera settings for the lens focal length -- do you set the camera for 1.) the focal length of the telescope or 2.) for the expanded focal length due to the 1.5x sensor in the camera, i.e. 1,250 mm for a 1,250 mm lens or the expanded length of 1,875 mm because of the camera's sensor at 1.5x [1,250 mm x 1.5]?
How long of a period of time did you expose each of the shots of the nebula; and, what settings on the camera did you use to do accomplish it?
I am hoping to get away to the California desert next weekend and give it a try on my C8 -- maybe at the Moon and the Ring Nebula.
A lot of people confuse the focal length issue. The sensor size of the camera does not change the focal length of the lens or its properties! The crop factor (1.5) is the sensors size relative to a 35 mm sensor - the old film standard. It simply means that your image is a smaller portion of the field of a 35 mm sensor - 1/1.5 x smaller.
So the focal length settings are whatever the lens is - no crop factor to account for.
(The confusion arises because often people are comparing the equivalent fields of view. In this case you need a wider lens (shorter focal length) on a cropped sensor to get the same field of view.)
By the way, the K5 and K3 work great with the GPS unit (or built in on the K3 I think) which will help you camera track the stars, but more than 300mm may be too much. Worth looking into!