Sherwood Observatory, in Coxmoor Road, now features a 59-seat dome with an “immersive” 10m (32.8ft) diameter screen.
There is also an underground exhibition space in a converted Victorian reservoir, a science discovery centre, meeting rooms, classrooms, and a cafe run by the Academy Transformation Trust Further Education College as a student outreach project.
The attraction is a joint venture between Mansfield and Sutton Astronomical Society and Ashfield District Council.
Councillor for growth, regeneration and local planning at the council, Matthew Relf, said the interest in the attraction had been “phenomenal”.