NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2015 Dec 8, 16:37 -0500
If the moon is at the zenith (or very close) then its position as viewed from the center of the earth or from its surface DOES NOT CHANGE (appreciably if only close).
It is for this reason that the LD will be equal to the SD of the moon. There is no parallax.
{Thought I should clarify that point. Still looking for confirmation}
Brad
I think I may be able to answer my own question. Would those more knowledgeable please check me?
I asked "Why isn't the lunar distance equal to the SD of the moon"? My initial guess was that it should have been, but here is my better answer, seeking confirmation:
The lunar distance is calculated from the center of the earth, not from its surface! The observer is at the surface, which will cause parallax. Parallax moves the moon's position, from location as if viewed from the center of the earth, to location as viewed from the earth's surface.
Unless the occultation occurs right at the zenith, the lunar distance will never be equal to the SD of the moon.
Okay Experts...rip it to shreds!!
Brad
On Dec 8, 2015 1:56 AM, "Peter Monta" <NoReply_PeterMonta@fer3.com> wrote:This was a lucky snap through stratus clouds. Had only seconds to get it. Another bucket list item checked off ;-) 200mm lens, ISO 100, f8, 1/1000 sec, 10 MP, infinite focus, white balance daylight. Lightroom 5 enhanced.
Nice! 0.1 arcminute---hard to beat that with sextant. (I was clouded out unfortunately.)Cheers,Peter
