There are seven sources of error in the marine sextant. Of the four errors listed, which one is adjustable?

Correct Answer: Option D — Error of collimation

The error of collimation is caused by the telescope not being parallel to the frame of the sextant. This is one of the few errors that can be corrected by the navigator using the adjustment screws on the telescope collar. Other errors like centering or graduation are inherent manufacturing defects.