Question 830Navigation General

The correct answer is A) Adjust the horizon glass to make it parallel to the index mirror with the index set at zero. To remove the index error from a sextant, the horizon glass needs to be adjusted so that it is parallel to the index mirror when the index is set at zero. This ensures that the line of sight from the index mirror to the horizon glass is perfectly perpendicular to the plane of the sextant, eliminating any index error. The other options are incorrect because adjusting the telescope (B) or the horizon glass to be parallel to the sextant frame (C) do not directly address the index error. Adjusting the index mirror (D) would not remove the index error, as the horizon glass needs to be the reference point.