A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robin Jouan
Date: 2017 Sep 25, 03:00 -0700
Dear Antoine, dear All,
ASTROLAB is a old package (written in BASIC on 1995), and its integrated ephemerids did not pretend to be 0.01 accurate! Most often, I use external ephemerids. But internal ephemerids are convenient for immediate results.
Thank you for your details about intermediate orbit parameters and precession-nutation values. Certainly, I will check mine when I have time to do so. I think the main differences about GHA & Dec (0.1' order of magnitude) come from the fact that ASTROLAB is accurate for Aries, but its background sky is shot at a given date, and updated only every 5 years. It was possible to improve it, but users told me that they like to use it as it was (only 450 kBytes with data base and documentation).
The most important for me is the sight reduction method, without any AP, and that is the reason why I answered to Ron's problem using his GHA+Dec own pairs. So results do agree, obviously.
Now, I am working about satellites + landmarks direct hybridation, using Matlab for allgorithmics validation. The question of celestial ephemerids is no longer addressed.