NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2012 Mar 25, 05:14 -0700
I recommend this NGA on-line calculator for ex-meridian reduction:
http://msi.nga.mil:80/NGAPortal/MSI.portal?_nfpb=true&_pageLabel=msi_portal_page_145&calcCode=01
Go to and click on ALTITUDE FACTORS AND CHANGE OF ALTITUDE
Enter with degrees and tenths of assumed latitude and declination of the body then enter meridian angle converted to time from meridional passage in minutes and tenths of time. The calculated result will be the correction in minutes of arc that is added to (Ho) of body near upper transit. The corrected (Ho) can then be reduced as an LAN or meridional passage to get Latitude at the time of observation.
(see attached pic 81 for example)
Greg Rudzinski
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