NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunar distance calculations
From: Ken Harris
Date: 2022 Mar 12, 19:47 -0800
From: Ken Harris
Date: 2022 Mar 12, 19:47 -0800
Mmmm. Which "Frank's Lunar Analyzer" are you using ? What latitude are you using ? I see you say "Abbreviated output for N39.0 W122.0", but my software defaults to N38. If I use N39, it's within 0.2 arcminutes of "Frank's Lunar Analyzer" :
python cel-nav-skyfield.py -t 2022-03-11T22:33:13 -g 39,-122,0 | grep -e semidiameter -e separation_from
# semidiameter(apparent) : 0.0
# semidiameter(apparent) : 14.9
# apparent0.separation_from(apparent1) : 29deg 19' 21.9"
# separation_from minus semi-diameters : 29deg 04' 27.5"
What "height of eye" are you using ?
I have skyfield version 1.42. Numpy v. 1.21.5-1. Python 3.10. Fedora 35 !
Strangely, if I use N38, I get a result that is 0.2 arcminutes different than yours (perhaps due to skyfield, numpy, python or OS differences) :
python cel-nav-skyfield.py -t 2022-03-11T22:33:13 -g 38,-122,0 | grep semi-
# separation_from minus semi-diameters : 29deg 05' 10.9"
If I modify my program to display "Geocentric Lunar Distances", it agrees with https://clockwk.com/apps/predict exactly : https://pastebin.com/1uBaGpAe
