Starship Asterisk*

So I think you are saying this: No, a star isn't "really" a point source, but since these telescopes aren't resolving the disk of the star, that's moot. The angle cut by the star is less than a pixel. What is happening is that both bright and dim stars are being spread by this Airy Disk ef...

Why are stars different sizes in astronomical photos? I assume that at interstellar distances, they are all point sources. Yet in a typical APOD picture, you'll see widely varying sizes. I thought perhaps it was due to atmospheric effects spreading the stars over a larger area ("twinkling"...