A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2019 Oct 9, 07:56 -0700
Appendix H pages 697 - 699 of the 1981 Bowditch vol. 2 does a decent job of correcting Nautical Almanacs that are multiples of 4 years out of date. For the Sun GHA and declination use the quad correction for the needed date multiplied by the number of four year multiples out of date (example: the 2007 NA would use Sun look-ups summed with the quad correction x 3 for use in the year 2019). For Aries use the column D value of appendix H for the number of 4 year multiples to sum with the out of date NA Aries look-up (example: the 2007 Aries correction value would be +5.5' for use in the year 2019). For star SHA and declination corrections multiply the annual correction in appendix H by the total number of years the NA is out of date.
Why not keep a photo copy of Bowditch appendix H with out of date Nautical Almanacs as a useful book mark.