Taking a Trip to Hawaii.. the Big Island

Ok, I'm going to Hawaii in early November. Mainly the Big Island (Hawaii). What stuff is a "must see" besides the telescopes? So far I've planned to see Volanoes Ntl Park also. Would it be a good idea to take a flight to another island, or is there too much to do on any one island? I'll be there for 8 days.

Sunrise from the summit of Haleakala (Maui) is well worth a trip. The volcano is awesome as well if you like to hike.

Just don't do like my friend did and get talked into buying a timeshare there at some high-pressure sales pitch. Or you won't be buying any telescope stuff for a while. :-)