# NavList:

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

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Re: Longitude by unequal altitudes - Brent
From: David C
Date: 2020 Jul 6, 19:53 -0700

Lars wrote

(h1+h2)(h1-h2) = h12 - h2 and the dimension of C is arc/time2 as seen in the bottom equation on the left-hand page.

Thanks.

My maths is very rusty.......

(h1+h2)(h1+h2) =( h12 + h22) + 2 h1  h2

(h1-h2)(h1-h2) =( h12 + h22)  - 2 h1  h2

but  (h1+h2)(h1-h2) = (h12 - h22 )

I note the correct dimensions for C.

This is a good winter method for noon  lat & long when using an AH. Noon sights can be taken but as the local hour angle increases the Sun's altitude becomes too low and AH sights are impossible.

In summer noon Sun sights are impossible with an AH but sights with the sun near or on the prime vertical are possible. I wonder if there is a method for finding lat when the sun is near the prime vertical?

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