Despite having all the necessary papers, and having a mounted telescope, it's not showing me any of the lesser constellations when I look for them in the night sky, despite saying that I've at least seen them on their respective papers (they show what moon phases they're most visible on.)

I'm playing with the Horizons 3 modpack on FTB, so I'm not sure if this is mod interaction or what.

Attune yourself, it's basic progression lock.

Is your telescope open to the sky above it?
Are there no blocks nearby (blocks adjacent to the telescope or too close can cause no stars to show at all)?
Are you seeing any stars at all or a blank screen?
Are you able to find any constellations (like the bright ones)?

they show what moon phases they're most visible on

despite you not having discovered them yet? Well, that's something i gotta fix...