# NavList:

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

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Re: Basics of computing sunrise/sunset
From: Christian Scheele
Date: 2009 Jun 17, 23:07 +0200
Right, and 34 minutes is refraction. Makes + 50 minutes in total to give 50/60 = ca. 0.83 degrees. If I don't hear from you I'll assume you agree and I'll begin to dissect my equation.

Thanks,

Christian Scheele
----- Original Message -----
Sent: Wednesday, June 17, 2009 10:51 PM
Subject: [NavList 8674] Re: Basics of computing sunrise/sunset

16 minutes is the half diameter of the sun?

On Wed, Jun 17, 2009 at 4:41 PM, Christian Scheele wrote:

I'm trying to solve the following sunrise/sunset astronomical triangle and
am encountering unexpected pitfalls.

cos(LHA) = [sin (a) - sin (lat) sin(dec)]/ cos(lat)cos(dec)

where I am assuming a = -0.83 degrees

It is of course something very basic and I'm almost embarassed to say that
although I keep rechecking what I'm doing, I remain with an error of about
15 minutes by the time I get to the final result in mean zone time. Before I
drag everybody into it, could somebody please tell me whether there are any
snags that I should look out for?

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