Rising and setting celestial bodies can be used to check for compass errors. In spreadsheet amplitude.xls enter whether the body is rising or setting in cell B1, the ship's latitude goes into cell B2, and cell B3 takes the declination of the body observed on the celestial horizon. The calculated amplitude in cell B4 inherits its sign from the declination input in B3. The calculated azimuth from cell B5 can be compared with the one observed and thus used to determined the error of that compass.

Summary for spreadsheet amplitude.xls:

Input cells: B1, B2, B3

Output cells: B4, B5