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    Re: Bowditch long term almanac
    From: Örjan Sandström
    Date: 2012 May 18, 16:57 -0700

    yes the astronomy website, also it was a 1956 version i atached, i got hold of the 1972 version later. this page is one of the few I have not seen a troll on.

    >The annual corrections for the stars will not change much over the years
    > But the quadrennial corrections for the sun certainly will - and they will >depend on the chosen period of validity, as I have stated. If the 1954 >Bowditch has the same quadrennial corrections as the 1981 Bowditch has, then >it is as I suspected and the older corrections were shipped wholesale to a new >epoch, which is not a valid procedure.
    ah, ok, that is good to know, the sun data he sent me seem to correspond fairly well with what was in the 1972 version, but as it had only one decimal point...
    the 1956 version is different.

    > My method was really quite simple - if time consuming. I used the Nautical
    >Almanacs for 1996 to 1999 as my starting point for the GHA and Dec of the sun.
    >I then used the "Stormy Weather" software program (which contains the full set
    >of astronomical algorithms, see http://www.stormy.ca/ ) to predict what the
    >GHA and Dec of the sun would be for each day during the years 2036 through
    >2039, which is ten quadrennial cycles later than my starting data set. Taking
    >the difference for each day between the two data sets and dividing by ten, I
    >arrived at the quadrennial corrections I use in my LTA. I used a similar
    >approach for the stars.

    I did use the NA to get GHA and Dec for the dates in question for the years 2008-2011,
    if I was to mimic you I need to get the same data as accurate as I can 40 years later (2048-2052) and divide differences by 10.
    wonder what data I would get if I followed your procedure (it would be 3 quadrenial cycles later than your set).

    it would require quite some time as it would take over 500 entries, perhaps next winter...

    oops, just came to think of a tiny problem, as all parts of the 4 year sun cycle use same correction in this almanac, I guess it would have to use some kind of middle ground for the correction to gha and declination, what would you sugest?, median? average? use correction for middle of cycle?

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