NavList:

Andrew,

An alternate method is to determine the GHA for 1200 zone time then apply (+/-) the assumed longitude followed by an arc to time conversion for time of MP. Adjust the assumed position for the new time of MP then repeat the calculation.

Estimating MP to within a couple of minutes is generally good enough for latitude determination so why not use the MP time to the nearest minute as provided in your attached table and adjust time for the difference between zone time longitude and the assumed longitude just as is done for determining the time of sunrise, sunset, and twilights.

Example for today at my current location 34* 10.5' N 119* 13.8' W

NA daily page MP 11H 54M. Observed MP will be 57M 00S later (PDT). Time of MP 12H 51M (PDT)

Alternate method:

GHA for 19:00(ZD+7) 106* 25.2' - 119* 13.8 W' = LHA 347* 11.4' = (t) = 12* 48.6'
12* 48.6' = 51M 14S later = 12H 51M 14S (PDT) MP

Greg Rudzinski
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