NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: No Lunars Era
From: Frank Reed CT
Date: 2004 Dec 6, 19:32 EST
From: Frank Reed CT
Date: 2004 Dec 6, 19:32 EST
Ken M wrote:
"I have to do a lot of
double checking to eliminate errors but I think that in the days when log
tables were in common use and arithmetic calculation was heavily drilled
at school, a lunar could easily be done in 30 minutes by an experienced
navigator."
double checking to eliminate errors but I think that in the days when log
tables were in common use and arithmetic calculation was heavily drilled
at school, a lunar could easily be done in 30 minutes by an experienced
navigator."
I agree that they could be done with relatively little time. I would say 20
minutes with a little experience, but the idea that this was "common math" I
don't believe at all. The only thing a navigation instructor could take for
granted in his students was knowledge of basic addition and subtraction. But
really, that's all you need. Sometimes a blank slate is easier to work
with.
And:
"Confidence in the result would come from comparing the lunar longitude
with the ded reckoning."
Ded instead of dead? That might be another interesting topic for
discussion.
But to your point, the comparison with the DR longitude was the ONLY way
that navigators could get confidence in their results and sometimes too much
confidence. It's easy to subconsciously "adjust" lunars, both in the
observations and the calculations. How often did navigators work back through
their calculations and find an error when none was present in order to bring
their lunar longitude into line with their DR longitude?
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
[ ] Mystic, Connecticut
[X] Chicago, Illinois