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    Re: V-Correction for Sun? Answer from UKHO...
    From: Gary LaPook
    Date: 2016 Oct 14, 23:43 -0700

    Just like the NA the Air Almanac was designed to provide the appropriate level of precision necessary for the type of navigation, inflght celestial navigation so it eliminates interpolations and provides the data only to a precision of whole minutes of GHA and declination (in the normal practice) thus speeding up computations. Since the accuracy of in fllight observations is in the order of several minutes it would be of no purpose to provide the data to a higher level of precision. It does provide a way to determine GHA sun and Aries to a tenth of a minute for use with astro-trackers which can track stars to a higher level of precision than a can a bubble sextant. 

    Also of interest, at the bottom of each column is tabulated the actual rate of hourly GHA and declination change but no mention of these tabulations is made in the Almanac and these could be used in place of a "v" or a "d" correction but this level of sophistication is not warranted for flight navigation and no interpolation tables are provided to allow utilization of these tabulated values. See attached sample page of AA.



    Well that’s a relief.  I really was beginning to wonder if I’d been doing it wrong all those years.  However, I’ve just waded through all 909 pages of the current US Air Almanac and was unable to find one mention of ‘v correction’, so that explains it.  The ten minute spacings must make it unecessary.  Incidentally, it still contains some great star diagrams and duration of twilight diagrams. Unfortunately, it’s not easily available in the UK except on-line, and if it was, it must weigh a ton. DaveP



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