For five years, the white fibreglass dome atop Dover-Sherborn High School has served upper-level astronomy students as a unique portal to the stars. Literally. Housed within this rooftop structure is a 12-inch Cassegrain telescope that is programmed to locate hundreds of astral entities in the moisture-ridden northern hemisphere. With a little structural tweaking this summer, the high schools mini-observatory will soon be ready for bigger things, said astronomy teacher Joshua Bridger.