Quicker Ex-Meridian Formula

This modified ex-meridian formula saves a few moves on the K&E slide rule (solution time 50 seconds).

Slide Rule:

a = (Cos Lat. Cos Dec.) / Sin (Lat. +/- Dec.)***      
(+) contrary name  (-) same name  *

+XM' = .524 (a)(t)(t)      
t = meridian angle in degrees and tenths  **

Calculator:

+XM' = (a)(t)(t) / 1.91

notes:

 * The (a) value can be worked up prior to observation. 

** Slide rule tip - pencil mark the slide C scale at .524 for quick cursor set.
*** Cos (Ho) can be substituted for Sin (Lat. +/- Dec.)   Ho = corr. sextant altitude

+XM' = ex-meridian minutes of arc to be added to Ho then solve as a LAN observation.

Sextant Lanyard

A sail tie makes for a comfortable sextant lanyard when worn Robinhood style. This frees up both hands for the sailor while keeping the sextant securely close to the vest. Loop the sail tie through the sextant handle then figure eight the ends together.

Latitude by Polaris

Sum the Q correction with the corrected sextant altitude (Ho) of Polaris to quickly determine north latitude.