My first telescope was a ten inch dob. I use all that I have weather allowing. You either have the desire to see what's up there or you don't. It's pretty tough to beat ten inches of aperture for a first telescope, he's 25 years old and has been warned about the size.
He's spending $600.00 on the ten inch. What Go To are you recommending in that price range? (I'm not disagreeing with your points on the 8 inch, but my first scope was a ten)
For GoTos I'm recommending a Celestron NexStar 4/5/6SE, depending on what he can find that meets price expectations. Certainly a brand new 4 or 5SE meets the budget. My 6SE was $650 on the dot, but obviously that takes a bit of luck, it was an open Box deal from HighPoint (probably a return that the recipient never opened). It's a phenomenal, portable scope that tracks all night long.
I have a Dob too, it's an 8"... about 40 pounds, 20 in the tube, 20 in the base. I still wouldn't want to bring it down stairs, it lives in my garage. Honestly, I've looked through enough 10/12" Dobs to realize I'm not missing much (our club's main site is a Bortle 6 at the edge of a very large city that stares out into the darkness of the Everglades (assuming we're pointing west), but our remote areas in the swamp are Bortle 3. While the 12" shows a difference on DSO, I don't see the difference when comparing 8 to 10" Dobs.
I understand he's 25, I was too... I also moved 5 times in 5 years, 3x chasing promotions, once for marriage, then into our house. I happen to think if you're going to go big, you should go trussed 12" at least with push-to if not go-to... but I wouldn't recommend it for beginners.
Edited by Hexley, 01 March 2021 - 12:08 PM.