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<blockquote data-quote="Whiskeyman" data-source="post: 572710" data-attributes="member: 13556">I've shot the Milky Way with an FX format camera and a 28 mm lens, and I wanted more field of view, such as with a 20mm.&nbsp; With a DX camera, I'd likely want a 10 to 14 mm lens.&nbsp; At that&nbsp; focal length, having a fast lens isn't that important for night sky photography because of the 500 rule, which is that you divide the focal length of your lens into 500 and that gives you your approximate longest possible exposure time in seconds.&nbsp; A 20mm lens gives a 25-second exposure, and a 10 mm lens gives a 50 sec exposure before the individual points of light start to appear as other than points of light.&nbsp; All other things being equal, you'll likely need to to divide your exposure time by the sensor size ratio for clean shots.Since your exposure time can be so long, a super fast lens isn't critical, especially when you are shooting at f5.6 or smaller, as you might be likely to do, to improve image quality.Good luck with your search for the right lens, and with your shooting.&nbsp; Let us know how your shooting the night sky is going by posting some of your shots here.WM</blockquote>

[QUOTE="Whiskeyman, post: 572710, member: 13556"] I've shot the Milky Way with an FX format camera and a 28 mm lens, and I wanted more field of view, such as with a 20mm. With a DX camera, I'd likely want a 10 to 14 mm lens. At that focal length, having a fast lens isn't that important for night sky photography because of the 500 rule, which is that you divide the focal length of your lens into 500 and that gives you your approximate longest possible exposure time in seconds. A 20mm lens gives a 25-second exposure, and a 10 mm lens gives a 50 sec exposure before the individual points of light start to appear as other than points of light. All other things being equal, you'll likely need to to divide your exposure time by the sensor size ratio for clean shots. Since your exposure time can be so long, a super fast lens isn't critical, especially when you are shooting at f5.6 or smaller, as you might be likely to do, to improve image quality. Good luck with your search for the right lens, and with your shooting. Let us know how your shooting the night sky is going by posting some of your shots here. WM [/QUOTE]

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