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    Re: Longitude by observation of the Sun, 19th Century
    From: Bill Noyce
    Date: 2013 Jun 13, 04:25 -0700

    Good explanation, but I think there's a typo in the following -- P and Z should be swapped in one spot:

    > The actual calculation that yields LAT from the altitude is the most basic spherical triangle
    > problem. Draw the ZPS (zenith-pole-Sun) triangle. The angle between the arcs ZP and ZS is the
    > local apparent time that we're looking for. The arc PS is the Sun's "polar distance" (90 +/- Dec).
    > This is a known quantity from almanac pages. The arc ZS is just the zenith distance: 90
    > Corrected Alt. We know this because we have measured it. And finally the arc ZP is the co
    > latitude: 90 - Lat.

    Corrected text:

    The actual calculation that yields LAT from the altitude is the most basic spherical triangle problem. Draw the ZPS (zenith-pole-Sun) triangle. The angle between the arcs PZ and PS is the local apparent time that we're looking for. The arc PS is the Sun's "polar distance" (90 +/- Dec). This is a known quantity from almanac pages. The arc ZS is just the zenith distance: 90 -Corrected Alt. We know this because we have measured it. And finally the arc ZP is the co-latitude: 90 - Lat.

    -- Bill N


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