Ok, I've done some checking and I can confirm for you that there are at least two different composites of the first shot. There are any number of reasons why this may have been done, most likely having to do with crawl issues, but the matte painting, starfield and foreground ships were optically composited in the printer at least a couple of times, leading to variations in versions. I'm not 100% sure, but I will be once I finish checking, but it appears that both versions here use the same starfield, only one of them is reversed horizontally and slightly higher up.

That is, that "Y" shape appears about halfway between the moon and the horizon of Tatooine in one version, but flipped and much closer to the horizon in the other version. I think some of the other differing patterns in star intensities is due to the fact that it's an organic, imprecise optical composite and not a digital composite, so you get different looks as the light actually passes through the system. I'll do a more thorough comparison, but if you want to check yourself, go find the part of the shot before the Star Destroyer comes in and identify the Y shape, then do the requiste flipping and repositioning in Photoshop to see if they match. No matter how you cut it, this shot was composited at least twice.

_Mike