The many things marked PGC_____ are tiny (to us) galaxies that are much further away. Next to each catalog number is a little circle or cross point showing the location. In some you can actually see a tiny oval or dot.
M31 is 2.537 million light years away. The tiny ones are probably 50 to 100 light years away, maybe further.
I got inspired to start looking for these when I saw a Tweet by OG astro-man Jack B. Newton, of the pic below. It’s a section of his photo of M45 where he had manually found and circled a bunch of these little gems. I was amazed, called him, and chatted a bit. That started me looking for them everywhere. I can find most of these in my pix of M45 too, even though I’m new to all this (4 months) and my shots aren’t as good.
I think part of the reason Jack is able to find all these is BECAUSE he’s old-school…. He doesn’t do any star reduction. Star reduction is done in most modern astro photos, to let you see the “target” better. But it eliminates some of these because they’re so small, the algo thinks they’re stars. Jack condsiders ALL of it the “target”, he just takes pix in a Bortle 1 with a giant scope, and processes them with, as he put it “very simple tools.”
These little gems just show me how vast the universe is, and how stunning it is that I can find them from my backyard with a DSLR, scope, and mount. It’s an almost religious feeling to me, and I’m agnostic.
Some men buy a sports car and have an affair for a midlife crisis. My midlife crisis is searching for distant galaxies.
Here’s Jack’s photo: