Muscat's planetarium, run by Petroleum Development Oman's Knowledge World, is a compact science stop rather than a major museum. It is useful for families and for travellers who want a break from forts, souqs, and beaches while still learning something rooted in the wider region.
The best reason to go is the connection between astronomy and Oman's desert skies. Shows and opening arrangements can change, so confirm ahead, but when it is operating it adds a thoughtful, cool indoor pause to a Muscat itinerary.