I made my Shed to be a roll off Observatory roof but I made the roof inside to be the night sky with 450 LEDS.
It looks like fairyland inside at night and when the roof is back it goes over my secret seating area. The 4 constellations of the stars are accurate to the night sky on one particular night of the year, so it could be classed as a planetarium. When the roof is rolled back it then becomes an observatory. The secret area then becomes the planetarium. Where can you go and see stars every night in the UK!!! I started this in June this year with 95% reclaimed materials which were being scrapped. The roof lights are run on solar panels, insulation is all old bubble wrap, so besides 6 sheets of ply to cover the inside, about 700 screws and a lick of paint everything else was free (excluding the telescope).