Best I got a couple of times was going to Pulpit Rock Observatory outside of Allentown PA. I can't remember the name of the type of scope my brother-in-law was using, it belong to the astronomy club he was a member of but I remember it was housed in not in a large rotating dome but it was in a type of large holding case that opened and the scope was mounted on a secure platform and had a 360 degree rotation. Saw the polar ice caps on Mars in beautiful detail. Just amazing. Was even on one memorable night able to see a very distant Neptune. A beautiful robin's egg blue as I remember .
If you could see the Martian ice caps in detail it must have been an impressive ‘scope!
Depending on conditions, I can just barely detect them.