NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Precision of lunars
From: Frank Reed CT
Date: 2007 Apr 24, 02:43 EDT
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From: Frank Reed CT
Date: 2007 Apr 24, 02:43 EDT
Alex, you asked:
"do you object his statements about the accuracy of the lunars
that I cited?
If yes, what are your corrections to these statements,
and what evidence can you give to support them?"
that I cited?
If yes, what are your corrections to these statements,
and what evidence can you give to support them?"
Lord Kelvin's comments, I would say, accurately describe the accuracy of
typical lunar distance observations around 1815 --combining the effects of
observer error, sextant error, and almanac error. They do not apply today.
Evidence? My own lunars. The lunars that a group of us did at Mystic in
September, 2005. The lunars I've seen beginners shoot when they have a
well-adjusted sextant in their hands. Etc.
You're still not getting very good results, and you're content to believe,
following Kelvin, that angles cannot be measured to better than 0.5 minutes of
arc accuracy with a sextant. Looking with a 7x or 10x telescope, an angle
that large is very obvious. With the limiting resolution of the human eye
(corrected) somewhere around 0.7 to 1.0 minutes of arc, the limiting resolution
through a ten power telescope is around 0.1 minutes of arc. So we can certainly
"see" angular shifts smaller than 0.5 minutes of arc. What's your latest theory
on the reasons you've been unable to do as well as you would like with your
observations?
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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