The bottom of the DMO is the visible part. For installation, demonstration and occasional maintenance, the interior must also be accessible. As not every ceiling can be approached from above, the entire planetarium must be able to descend.
Press PLAY to play the movie.
It was easier for Eise Eisinga. He also had to be able to reach the top, but he had access via his attic.
The DMO on the video is attached to a flat roof, so no attic to gain access. That is why the elevator option was chosen, an electric winch lowers the DMO so that work can be done on the inside.