Question 1691Navigation General

The correct answer is C) hs to the sensible horizon. When taking a sextant observation, the sighted sextant angle (hs) is the angle between the celestial body and the visible horizon. However, the visible horizon is not the same as the sensible horizon, which is the true horizon taking into account the effects of atmospheric refraction. The dip correction is used to adjust the sighted angle (hs) to account for the difference between the visible and sensible horizons. Since the dip is a negative value, it is subtracted from the sighted angle (hs) to correct it to the sensible horizon. The other options are incorrect because option A) involves correcting the observed altitude (Ho) rather than the sighted angle (hs), option B) is not the correct correction to apply, and option D) refers to the visible horizon rather than the sensible horizon.