Artificial horizon

This "artificial horizon" can be used in cunjunction with a sextant to practise celestial navigation at home. Just print the parts and get hold of a pair of plain window glasses with a thickness of 2 mm and 125 mm * 125 mm length and width (I paid 4 € for both of them at the local glazier).

Stick the two sides (they are identical) in the respective holes in the bottom part and fill the bottom with 1 to 2 cm of some fluid. A viscous fluid (motor oil, molasses) might work better, but even water