Stars, Lenses, full frame senses ;)

[jake337]

This is why you need f/1.4:

Yup it's either F1.4 or equatorial tracker.

 

[Garbz]

Assuming you are still here and want a technical explanation to your answer, stars are bright, sky is dark, the two in combination result in that lovely thing we call chromatic aberration. CA is something a lot of cheap lenses do NOT do very well at the slightest when used wide open. Sure you can often stop the lens down to get CA under control but then why buy a wide lens in the first place when a cheap kit lens could do that too.

CA is a minor correctable annoyance in most normal photos but for stars it destroys the image. Stars are a wonderful set of funky shades from red to blue, and with a lens that has CA you end up with ... purple, and when you correct for it you end up with white blobs.


On an unrelated note that Ford Fiesta has more boot space than the Aston Martin. Even cheap things are good for something, but stars is like pitching them against each other at a racetrack.

 

[McNugget801]

I have the sigma 20mm f1.8 and it works wells