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    Re: Almanac for Computers
    From: Michael Wescott
    Date: 1996 Aug 29, 17:00 EDT

    John H Henderson wrote:
    > This brings another question to mind....do the almanacs/sight
    > reduction tables/computers take the oblateness of the earth into
    > account?  I figured out HO211, and it does not.  And since the
    > almanacs don't take your position into account, I do not believe
    > that they can either.
    There is no need. Longitude and latitude are astronomical, derived from
    actual or projected observations with respect to the local horizon.
    In other words, at a given spot latitude will be based on the angle
    that a perpendicular to the tangent plane makes with the equatorial
    plane.  This is not the same as the angle made by the equatorial plane
    and the line through the center of the earth from the spot.
    Only when distances are involved does the actual shape of the earth
    become an issue, and then, as a practical matter, only when the
    distances are fairly large (on the order of a hundred miles or so).
    	-Mike Wescott
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