What are the four main Sextant errors?

The four main errors associated with the use of a sextant are crucial for ensuring accurate navigation. Perpendicularity is an error that occurs when the telescope cannot be perfectly aligned perpendicular to the plane of the sextant's arc. This misalignment can lead to incorrect angle measurements, affecting the observed altitude of celestial bodies.

Each type of error has its own implications on the accuracy of sextant readings. Side error arises when the instrument's optical components are not properly aligned during use, affecting observations when measuring angles from different sides of the sextant. Collimation error is related to the alignment of the telescope's line of sight with the graduated arc, leading to discrepancies in readings. Index error results from a misalignment of the index arm relative to the scale when the sextant is at zero, which can cause systematic errors in all subsequent readings.

Understanding these errors is essential for navigators to make adjustments and obtain accurate celestial measurements, directly impacting their ability to navigate effectively at sea.