# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: AM and PM time sights
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°

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