# NavList:

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

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Formulas to Compute LHA
From: Andrew Corl
Date: 2009 Jun 23, 09:25 -0700
All,

I need some help.  I am attempting to work the problem in Ocean Navigator using the Lapook-Bygrave Slide Rule.  I am uncertain how to compute the Local Hour Angle (LHA).

In the following cases I am assuming my longitude to be 77 degrees west of Greenwich.

1. The GHA of the Sun is 55 degrees west of Greenwich
2. The GHA of the Sun is 95 degrees west of Greenwich

In the following cases I am assuming my longitude to be 120 degrees west of Greenwich

1. The GHA of the sun is 170 degrees east of Greenwich.

Also what is the formula if my position is east of Greenwich and the sun has a GHA of more than 180 degrees?

Thanks
Andrew

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