NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sun sights during an eclipse: "bad limb" calculation
From: Paul Hirose
Date: 2023 Oct 17, 11:52 -0700
From: Paul Hirose
Date: 2023 Oct 17, 11:52 -0700
On 10/16/2023 5:11 AM, NavList Community wrote: > This conclusively indicates that there is a significant bug - i.e. > significant to their number of digits published for Sun and Moon > Diameters - in the */JPL Horizon Software/*. Refracted Sun and Moon > Diameters values are not equal to their unrefracted counterparts as > incorrectly showing from the */current JPL Horizon Software/* results. In defense of JPL, it's not possible for Horizons to calculate refracted semidiameter. That depends on the position angle on the limb. But there's no way to input that angle to Horizons. To use round numbers (altitude 50°, semidiameter 16', temperature 10 C, pressure 1010 mb), the contraction of the limb at position angle 180 (6 o'clock on the limb) is 0.46". But at PA 90 or 270 it's 0.27", or 40% less. -- Paul Hirose sofajpl.com
