NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Quicker Ex-Meridian Formula for Slide Rule or Calculator
From: Greg Rudzinski
Date: 2016 Nov 29, 11:08 -0800
From: Greg Rudzinski
Date: 2016 Nov 29, 11:08 -0800
This modified ex-meridian formula saved a few slide rule moves on the K&E (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.
+XM' = ex-meridian minutes of arc to be added to Ho then solve as a LAN observation.
Greg Rudzinski
