NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: additional planet corrections...
From: Chuck Taylor
Date: 1999 Nov 23, 4:50 PM
From: Chuck Taylor
Date: 1999 Nov 23, 4:50 PM
On Tue, 23 Nov 1999, Russell Sher wrote: > Does anyone know why the additional altitude corrections in the nautical > almanac are needed for Venus and Mars at certain times of the year? Is this > for refraction? Russell, Mostly for parallax. The Sun, Moon, Venus, and Mars are the only bodies close enough to earth for parallax to be a factor. Parallax for the Moon is treated separately. For the Sun, there is about 0.1' built into the main correction for altitudes up to 60 degrees. In the cases of Venus and Mars, whether or not we are close enough depends on whether we are on the same side of the Sun or opposite sides of the Sun (which depends on time of year). If on opposite sides, the distance is too far for parallax to matter. Jupiter, Saturn, and the stars are always too far away for parallax to matter. Cheers, Chuck ---------------- Chuck Taylor SEASCAPE GB 32-2 Everett, WA, USA
