>>4334075Wider is not always the best when it comes to this application, though it helps in keeping things simple. You most certainly get to expose longer with a Wide Angle, and that is worth something, but it's less worthy than actual aperture diameter in combination with the aperture speed. Say, a 15mm f2 offers a ratio of 15/2=7.5. A 24mm f1.4 offers a ratio of 24/1.4=17. You'll get way, way more light and resolve way more of the milky way with a 24/1.4 even if you expose for a shorter time. An extreme example would be, I dunno, 85/1.8 = 47. Obviously its FOV is not applicable for milky way, but for the area the 85mm will gather its light, it will gather 6x more light than the 15mm f2. Again, obviously not applicable if you want to simply capture a nice milky way, we're entering deep space astrophoto area, but you'll notice on
astrob.in or on other website that more often than not, the best milky ways are often a product of 24/1.4 lenses or very fast 35mm lenses. Rarely from UWA lenses (though they offer you more leeway to play with a background/an interesting subject). This is because longer focal length lenses will resolve way more light from the milky way than a wide angle, even at f2 or f1.8. The caveat is you'll have to do stitches, compared to a wide angle giving you a single shot (but with a less pronounced milky way). And then add-in stacking on top of that to reduce noise, and one can see why one shouldn't go with a too long focal length, it becomes nightmarish.
I think a very fast 24mm is a good compromise between light collection, time exposure, stacking, and pano stitches you may or may not have to do to resolve a very detailed milky way.
