NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Moon question
From: Frank Reed CT
Date: 2006 Jul 23, 06:30 -0500
Guy, you asked:
"The question is it OK to interpolate here"...
Yes. Bear in mind that you are getting close to the reliability limits of
the data in the Nautical Almanac --approximately one-quarter of a minute of
arc. Because of this limiting factor, it is not strictly necessary to
interpolate in the Moon correction table, and your results may not be better than if
you were to skip the interpolation, but it won't do any harm.
A more obvious example of the accuracy limits for these tables would be the
Sun altitude correction tables. Suppose the Sun is 25 degrees high on March
31st. According to the tables (on the inside cover of the Nautical Almanac),
the net altitude correction is -18.1 minutes for an upper limb sight. The next
day the correction for the same sight is -17.8. This sudden change is not
real. It is an artifact of the way the tables are constructed, and it's plenty
good enough for most practical work.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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From: Frank Reed CT
Date: 2006 Jul 23, 06:30 -0500
Guy, you asked:
"The question is it OK to interpolate here"...
Yes. Bear in mind that you are getting close to the reliability limits of
the data in the Nautical Almanac --approximately one-quarter of a minute of
arc. Because of this limiting factor, it is not strictly necessary to
interpolate in the Moon correction table, and your results may not be better than if
you were to skip the interpolation, but it won't do any harm.
A more obvious example of the accuracy limits for these tables would be the
Sun altitude correction tables. Suppose the Sun is 25 degrees high on March
31st. According to the tables (on the inside cover of the Nautical Almanac),
the net altitude correction is -18.1 minutes for an upper limb sight. The next
day the correction for the same sight is -17.8. This sudden change is not
real. It is an artifact of the way the tables are constructed, and it's plenty
good enough for most practical work.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
