NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunar4.4. vs Frank's online calculator
From: Paul Hirose
Date: 2023 May 5, 00:27 -0700
From: Paul Hirose
Date: 2023 May 5, 00:27 -0700
On 5/4/2023 1:16 PM, NavList Community wrote: > I would like to ask a question: How do you evaluate the accuracy of the > results from your Lunar4.4 program? For example +/-0,1'; +/-0,05' or > maybe +/-0,01'? See the "Tests" section in the Lunar 4.4 page: http://sofajpl.com/lunar4_4/ Also you can try the planetary and stellar reduction examples in the 2019 Astronomical Almanac: https://archive.org/details/binder1_202003/page/n183/mode/2up?view=theater The Almanac examples are reductions to geocentric apparent place. For a topocentric example, see this page by Patrick Wallace: https://syrte.obspm.fr/iauWGnfa/ExPW04.html This is a difficult test, but Lunar has a place for every input except the very small IERS X,Y corrections (+0.038,-0.118 mas). Be careful when you enter the star data. The default epoch in my program is J1991.25 (epoch of the Hipparcos catalog). You must change that to 2000.0. Don't forget to check the RA "degrees" box. His RA proper motion is great circle mas/year, which the same as the default setting of the program. The star is 0.2° from the zenith, so you can't separately compare azimuths and altitudes. An apparently large error in azimuth has only small effect on the direction of the star. You must compute the separation angle between the Wallace position and Lunar position. Lunar 4.4 should be accurate to about 1 mas in the Almanac and Wallace examples. -- Paul Hirose sofajpl.com
