These tours are free of charge , but do require a reservation. Reservations may be made by calling 321-2400 between 10 a.m. and 4 p.m. Tours begin at 8 p.m., and feature a slide presentation about the observatory and current astronomy, and a guided walking tour of the building and domes. If the sky is clear, tour participants may view the sky through the 13-inch Refractor . A special open house is held once a year, usually in the early fall. Even the Thaw .
Open house is free of charge but tickets are required and go fast .