Part III · The line of position · Page 7 of 8
A whole sight, start to finish
DR N 41°12′, W 064°30′. Sun's lower limb at 14h23m41s UT on May 14, 2027; after the sextant corrections, Ho 57°24.4'.
Almanac: GHA 30°54.6' + increment 5°55.2' = 36°49.8'. Dec N 18°39.8', d corr +0.2′ = N 18°40.0'.
AP: N 41°, W 064°49.8'. LHA = 36°49.8' − 64°49.8' + 360° = 332°.
Pub. 249, Lat 41°, Dec 18° same name, LHA 332°: Hc 56°46′, d +46, Z 125°.
Table 5 (d 46, 40′): +31′. Hc = 57°17′.
Zn: N. latitude, LHA over 180°: Zn = Z = 125°.
Intercept: Ho 57°24.4' − Hc 57°17′ = 7.4 nm toward, from the AP along 125°.
Because Pub. 249 gives Hc to the whole minute, intercepts are good to about a mile, well inside what a sextant at sea can deliver. In the practice, the gentle problems start from Ho, GHA and Dec; the full ones start from the watch and the sextant.