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Is this the astro thread? I have a question, I'm kinda new so forgive me if it's dumb. So far I only ever did milky way photography, with the classic rules of high enough ISO but not too much, max aperture or close to it, and 15 or 20sec of exposure depending of the focal length until it starts making trails. Okay, it gives good enough results, not great not terrible.
Then I stumbled onto "stacking" photos. If I get this right, I take a whole lot more of photos, and then stack them in software like Sequator or any equivalent. Meaning I can get less noise as I can use less high ISO. And I assume, I'm also get more light through stacking. Is that right?
My question is about numbers and equivalencies. Let's say we're using a full frame setup : 20mm f1.8 lens. Let's settle for 20sec of exposure at ISO 3200. And let's say I take a picture.
With stacking, how many pictures would I need to take to get the same picture taken above if I change the parameters to ISO 1600? Two pictures? Same question if I use ISO3200 but f2.8. 2 pictures as well? (as, unless I'm wrong, 2.8 gathers 2x less light than f1.8)? And then the combination of, I dunno, f3.5 at ISO 100. I assume I'll have to take 15 pictures or something.
Basically I'm trying to find the "conversion rate", if there's any. If so, stacking means I wouldn't have to buy an expensive wide angle fast lens, but could settle for wide but lest fast,, which is good for hiking. At the cost of staying there in the cold of the night more time that I would with a faster lens.
