A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2016 Jan 4, 00:46 -0500
Heavens, is that a 2102D. ;-)
For those that would like a go at a star ex-meridian Diphda and Ankaa are now in good position during evening twilight.
From: Greg Rudzinski
Date: 2015 Dec 31, 11:15 -0800
For a little fun on the final day of 2015 I did a time trial of the pocket trig calculator against the pocket 6" slide rule using the ex-meridian correction formula.
a = 1.964 (Cos Lat.) (Cos Dec.) / Sin (Lat. +/- Dec.) } contrary name + same name -
a(.267)(LHA t)(LHA t) = ex-meridian correction in minutes of arc added to Ho. The sum is solved as an LAN observation.
a= 1.964(Cos 34°10')(Cos 23°4')/Sin 57°14' = 1.778 by calculator 1.78 by slide rule
1.778(.267)(3.9°)(3.9°)= 7.22' by calculator 7.2' by slide rule
The calculator took 58 seconds with 57 button pushes.
The slide rule took 84 seconds with 6 moves of the slide and 6 moves of the cursor.
The calculator wins by only 24 seconds. Practical accuracy is even.
(Diphda-Anka-Near-Meridian.jpg: Open and save)