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: Geoff Hitchcox
Date: 2023 Oct 11, 21:05 -0700
From: Geoff Hitchcox
Date: 2023 Oct 11, 21:05 -0700
Hi Chuck,
Thanks for double checking the method.
The good news is that there is nothing wrong with your results - well done that man!
I just ran my code again *twice* - using "Standard Refraction" and also "No Refraction" using JPL Horizons for Moon and Sun positions in the sky.
==============================
2023-Oct-14 15:36:08.0 = First touch of Moon with the Sun. (Standard Refraction)
2023-Oct-14 15:36:11.5 = First touch of Moon with the Sun. (NO Refraction)
==============================
2023-Oct-14 18:51:10.5 = Last touch of Moon with the Sun. (Standard Refraction)
2023-Oct-14 18:51:08.5 = Last touch of Moon with the Sun. (NO Refraction)
==============================
So Chuck, you raise a good point, when comparing Eclipse times, is refraction accounted for?
This also makes my result much closer to Kermit's (if I use refraction).
I guess once we start getting down to doing seconds (of time) comparisons, we should be mindful that the Moon is not a perfect mathematical circle - but has topology, with mountains and valleys.
A worthwhile page to glance at is this one by Xavier M. Jubier, on limb profiles - a big deal to those doing Occultations by the Moon of Stars and Asteroids - getting way off topic here re Celestial Navigation.
In my brief look at eclipses, the best site I have found so far is by Xavier - Vive la France !
Thanks again Chuck, for drawing our attention to the role of refraction in comparing accurate Eclipse times!
Regards, Geoff Hitchcox, Christchurch, New Zealand
