system
Given the following post, respond as if you're commenting on Reddit:
human
I heard somewhere that if one could see the Andromeda galaxy in its entirety, it would look 2-3 times the size of the moon, is this true?

I can't remember where I heard it, but supposedly all we are seeing when we look at it through consumer grade optics is just the bright center. Is this true?
gpt
I've heard 6x as the number, but why don't we do a bit of calculation and figure it out?

The moon's angular size is about 32 arcminutes, which translates to roughly a half of a degree.

Andromeda is 2.5 million lightyears away and about 200,000 lightyears across. So its angular size if it was all visible would be arctan(200,000/2500000) which comes out to about 4.5 degrees. By that estimate, Andromeda could be up to 8.5x larger across than the moon in the night sky!