A marine sextant has the index arm set at zero and the reflected image of the horizon forms a continuous line with the actual image. When the sextant is rotated about the line of sight the images separate. The sextant has __________.

Question

Accepted Answer

Option C: side error. Side error occurs when the horizon glass is not perpendicular to the sextant frame, causing images to separate horizontally when the instrument is tilted about the line of sight.