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From: Frank R (no email)
Date: Fri Apr 08 2005 - 18:15:55 EDT
Bill, you wrote:
"A line perpendicular to a line through the horns points at the Sun? Had not
thought about using that to align the sextant. Thanks."
Yes, it's very useful. This instruction was included in Maskelyne's
instructions on lunars in the earliest Nautical Almanacs. You can read his
instructions and maybe get a feel for the early attitudes in the online scan of the
1805 N.A. on the Blunt-White Library web pages at Mystic Seaport's web site:
www.mysticseaport.org
And you wrote:
"Moon was approx. 53d, and dim against the sky. Given the Sun was lower, it
might have made sense to us it in the horizon glass instead of the Moon, but
it seemed easier to have the Moon in the glass as it was difficult to see."
This is probably another reason why navigators in the 19th century seem to
have avoided lunars when the Moon's elongation was less than about 50 to 60
degrees. The contrast against the sky is just too darn low. Of course, they
could have waited until dark and used stars if really necessary.
By the way, that mystery angle you were wondering about... it's the
difference in azimuth between the two bodies.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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