NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Refraction
From: Gary LaPook
Date: 2007 Nov 09, 02:09 -0800
From: Gary LaPook
Date: 2007 Nov 09, 02:09 -0800
Gary LaPook writes: Back in March there was a discussion of various formulas to use to predict refraction. I have found some other formulas that may be more precise. The U.S. Naval Observatory used to publish its "Almanac For computers" but stopped it after 1991. That publication has several formulas for refraction: (1) R' = cot(a + (7.31/(a + 4.4))) (2) R = R' - 0.06sin(14.7R' + 13) R is in minutes and a is the observed altitude. "At sea level, with air temperature of 10�C and pressure of 1010 mb, R' of eq. (1) is accurate to 0.07' and R of eq. (2) is accurate to 0.015' for an altitude range of 0� - 90�." "For nonstandard conditions the following formula is accurate to about 0.2' for temperatures in the range of -20� to + 40� C and pressures of 970 - 1050 mb. (3) R = R'((P - 80)/930)/(1 + 8x10 ^ -5(R' + 39) T - 10))) --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
