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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Basics of computing sunrise/sunset
From: Brad Morris
Date: 2009 Jun 17, 16:58 -0400
From: Brad Morris
Date: 2009 Jun 17, 16:58 -0400
Please note that you must consider the Equation of Time to convert from Apparent Time to Mean Time. Be careful about what you mean by sunset, there are many 1) Upper limb of sun touches the horizon 2) sun 6 degrees below horizon 3) sun 12 degrees below horizon 4) sun 18 degrees below horizon You must consider your offset in longitude from the center longitude of your time zone. That is, sunset occurs earlier in the eastern section of a given time zone than a sunset in the same time zone, but on the western edge! That should pretty much do it! Best Regards Brad -----Original Message----- From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Christian Scheele Sent: Wednesday, June 17, 2009 4:41 PM To: NavList@fer3.com Subject: [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? "Confidentiality and Privilege Notice The information transmitted by this electronic mail (and any attachments) is being sent by or on behalf of Tactronics; it is intended for the exclusive use of the addressee named above and may constitute information that is privileged or confidential or otherwise legally exempt from disclosure. If you are not the addressee or an employee or agent responsible for delivering this message to same, you are not authorized to retain, read, copy or disseminate this electronic mail (or any attachments) or any part thereof. If you have received this electronic mail (and any attachments) in error, please call us immediately and send written confirmation that same has been deleted from your system. Thank you." --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
