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    Re: 1901 May, 22 Lunar example by French Navy Captain Arago
    From: Paul Hirose
    Date: 2010 Jan 13, 11:53 -0800

    antoine.m.couette@club-internet.fr wrote:
    > Instead of
    > reducing the observed sextant distance between limbs into a gecocentric
    > Centers distance, Arago first only and simply reduces the sextant
    > distance into the topocentric apparent distance between refracted
    > centers. And then from CT (Connaissance des Temps) he works "backwards"
    > - as we would say - starting from its published (geocentric) equatorial
    > coordinates into "CT derived" topocentric apparent distances between
    > centers at two times (hopefully supposed to be) around the observation
    > time.
    My method is similar. I assume the topocentric separation angle and
    altitudes are linear functions of time, latitude, and longitude. Those
    last three quantities are the unknowns in three linear equations, which
    I solve. Of course the functions are not exactly linear, so the solution
    merely gives improved estimates of the unknowns. This is repeated until
    the result converges to the desired accuracy.
    About a year ago I described the method in more detail, and solved a
    real lunar:
    > One question though : are short limb distances still a limitation
    > nowadays with the powerful computation software available on line ?
    I have never tested my program with such an observation. If you have
    one, I'll try it.
    I filter out messages with attachments or HTML.

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