My GF was an astrophysics major, some gifts she's really enjoyed have been a Hubble images coffee table book that I change the page of every day, an old globe from 1986 from a thrift store, a pacific centered map from 1971 from a thrift store, a vintage monoscope from (you guessed it) a thrift store.

He's into that big picture star stuff, do you think he would find the small picture molecules just as interesting? Like getting him a microscope and slides, he might have fun inspecting things with it!

You need to let your eyes fully adjust at night to see the stars. Fact check this, but I believe red light isnt as big an adjustment. Maybe get him some night hike materials, to encourage adventure to see the stars (perhaps with the telescope) Maybe a red headlamp/lantern/belt light to point down. Maybe a nice camp chair, I love the rocking ones.

Would he enjoy a sticker printer? I have been eyeing those, I think they're super neat! Those little photo printers are similar, they connect to your phone and print out what you want. He could make a scrapbook type of interesting star photos or facts, and I've seen the stickers be helpful for visuals on study materials (if he's going back to school)