What must be done to the Index Error on a sextant when it is a positive value between 0-135?

When a sextant indicates a positive index error between 0-135 degrees, it means that the instrument is reading higher than the actual angle being measured. To correct this discrepancy, you will need to subtract the positive index error from the observed altitude. This adjustment ensures that you obtain an accurate measurement of the celestial body’s angle above the horizon, which is crucial for determining your position at sea.

Neglecting the index error, ignoring it, or recording it without adjustment would lead to significant inaccuracies in navigational calculations. Therefore, understanding that a positive index error requires subtraction is key to effectively using the sextant for navigation.