It's 1/72nd of the celestial sphere I think, since a single rotation gives you the east and west views in full, but due to the 90° field of view, you need to re

It's 1/72nd of the celestial sphere I think, since a single rotation gives you the east and west views in full, but due to the 90° field of view, you need to repeat that rotation in the north-south direction to cover the entire sphere.