The observatory hosts a Stargazing Night* every Saturday night! During the Sterrenkijk evening you view the and may join the Carl Zeiss telescope. During clear weather you can look through the telescope at the then interesting objects in the sky. But even during cloudy weather the viewing evening is well worth a visit, there is plenty to experience and do.
Tickets cost €9.00 and are available at: https://www.sterrenwacht-mercurius.nl/agenda/
The observatory is open from 1 p.m. on Saturdays. Stargazing, of course, is only after dark. The starting time of 7 p.m. is therefore approximate.