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Note that if( cos LHA > 1 ) there is No phenomena at the place(lat, lon)

The Almanaque N�utico, gives the following values for the zenith distance:

dz = 90� - Ho
Sun:
90.8    �   Sunrise/sunset
96  �   civil twilight
102 �   nautical twilight 
Moon:
90.57 + (SD-PHE)/60�    moonrise/moonset
Planets & stars:
90.57   �


Andr�s Ruiz
Navigational Algorithms
http://www.geocities.com/andresruizgonzalez




-----Mensaje original-----
De: NavList@fer3.com [mailto:NavList@fer3.com] En nombre de Christian Scheele
Enviado el: mi�rcoles, 17 de junio de 2009 22:41
Para: NavList@fer3.com
Asunto: [NavList 8673] Basics of computing sunrise/sunset


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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