Hello,
I'm about to buy a Sigma 20mm f1.4 Art for my astro timelapses. And I want to know at what f-number (f1.4 or f2) should I shoot. I'm wondering because I know there will be some coma at f1.4 but if I close the aperture at f2 there will be flickering (or will there?). I've never experienced flickering because I've always been shooting at f2.8 which is the max aperture with my current lenses and practically it doesn't close and open for every shot.
So, which one should I choose in your opinion?

What about trying it out and seeing what happens ? I doubt you'll get any issues because you will be doing long exposures which would probably iron out any small variations in the aperture flicker. Personally I don't use the full open on my lens because of the vignetting but then again I use manual lenses for star work. Tests are always the best way to go.

Steve