Question 1673Navigation General

The correct answer is C) 4°17.0'. To calculate the observed altitude (Ho), we need to apply the necessary corrections to the sextant altitude (hs) based on the given information. The corrections include index error, refraction, and dip. The index error of 1.9' off the arc needs to be applied to the sextant altitude (hs) of 4°33.0', resulting in a corrected altitude of 4°31.1'. Next, the refraction correction for a temperature of -10°C and a pressure of 992 millibars is approximately -0.7'. Finally, the dip correction for a height of eye of 42 feet is approximately -13.4'. Applying these corrections to the corrected altitude yields the observed altitude (Ho) of 4°17.0', which matches the correct answer. The other answer choices are incorrect because they do not accurately reflect the calculated observed altitude based on the given information.