NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Basics of computing sunrise/sunset
From: Christian Scheele
Date: 2009 Jun 18, 12:19 +0200
From: Christian Scheele
Date: 2009 Jun 18, 12:19 +0200
Greg, thanks for your input. Right, one really has to keep an eye on those trig functions which change sign going from one quadrant to the next. I was assuming a dip of zero, which is not realistic but not too serious because I often watch the sunset at the beach, sitting down almost at water's level. Christian ----- Original Message ----- From: "Greg Rudzinski"To: "NavList" Sent: Thursday, June 18, 2009 1:41 AM Subject: [NavList 8683] Re: Basics of computing sunrise/sunset Christian, Even though the altitude is negative enter it into the formula as positive. Add the second part of the formula if latitude and declination are the same name(north or south) and subtract if contrary. Be sure to apply the equation of time in the correct direction and the same goes for the arc to time correction for the angular difference between the longitude of the observed sunset and the time zone meridian. If sunset is before 1800 LMT add 180� to the formula angle. If sunset is after 1800 LMT subtract the formula angle from 360�. Dip is also a factor to corrected for. Greg On Jun 17, 1:41 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? --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---