6/20/2023 0 Comments Focal length on astrometry![]() even a fixed tripod can shoot reasonable 30-second subs using a 14mm lens at f2.8. This implies that there is always a short enough focal length and a fast enough focal ratio that any tracking mount can cope with, without autoguiding. Basically, even at the darkest sites on Earth you can get away with subs as short as 1-minute at f2.8, 2-minutes at f4, 4-minutes at f5.6, etc. A faster focal ratio means that you can use shorter sub-exposures and still have efficient stacking. A major advantage of camera lenses compared to most telescopes of similar aperture diameter is that camera lenses almost always have a faster focal ratio and a flatter image field (less-distended stars near the frame edges). any of the Canon 1.6x crop cameras like the 20D, 40D, 400D, etc). ![]() a Canon 1Ds or a 5D) and ending with a view using a 4000mm focal length C14 on an APS-sized DSLR (e.g. ![]() Yes, you can even take Deep Sky photos with no tracking mount at all! Anyway, below please find examples starting with a super wide angle view using a 14mm lens on a full 35mm format DSLR (e.g. Basically, the shorter the focal length you use, the easier it is to track the sky, and the cheaper the tracking-mount you can get away with. Over the years I have taken a number of images of DSOs (Deep Sky Objects) and I thought it's time I displayed examples of what is possible with ordinary camera lenses, as an encouragement to others, using a DSLR. No, you do NOT need a telescope to make satisfactory images of Deep Sky Objects, the stuff (star clusters, nebulae and galaxies) that lie well outside our Solar System.
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