Remember that before an observation is at all accurate, it must be corrected to make it a true altitude. Remember also that the IE must be applied, in addition to these other corrections, in order to make the observed altitude a
altitude. So there are really five corrections to make instead of four, providing, of course, your sextant has an IE.
Examples:
1. June 20th, 1919, observed altitude of
69° 25' 30". IE + 2' 30". HE 16 ft. Required
.
2. April 15th, 1919, observed altitude of