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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2016 Jun 28, 10:49 -0700
Dave,
Check your assumed 41°S 174° 44.4' E 21:00 UT pre-calculation. I get 10° 10' Hc, LHA 308° 59.2' which changes the TS calc results. Sumner 40°S 42°S should slop correctly ?
Greg Rudzinski
From: David C
Date: 2016 Jun 27, 20:27 -0700
I am having trouble with a time sight, which I am using to plot Sumner lines (by his original method). If I use a pseudo PM sight the Sumner line passes through my location. However if I use a pseudo morning sight the calculated longitudes are completely wrong and the Sumner line slopes the same way as the PM sight. This suggests that the problem is with W or E meridian angles.
Can someone please check my working which is as follows:
(a) Calculate Hc from pseudo sight.
27/06/2016 0900 NZST (+12)
26/6/2016 2100 GMT
GHA 134° 14.9'
Dec 23° 18.8'
Assumed lat S41°
Assumed long E174° 44.4'
LHA 309° 19.9'
Hc 11° 1.2'
Zn 46° 12'
(b) Calculate longitude for two latitudes to plot a Sumner line.
27/06/2016 0900 NZST
26/6/2016 2100 GMT
GHA 134° 14.9' 134.25°
