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    Re: Trying lunars
    From: David Iwancio
    Date: 2022 Sep 10, 01:52 -0700

    David:

    First, you probably mean 32' of longitude, not 32 mintues of time.  But one thing I like to keep in mind that being within 30' of longitude (2 min of time) was good enough to meet the gold standard of the British Board of Longitude.  If you're measuring to the nearest 0.1' on your sextant, the theoretical limit of your accuracy is going to be to the nearest 0.2 min of time (i.e.+/- 12 s).

    As for which limb to use when the moon is near full, if the almanac you're using doesn't tell you the instant of the full moon (which the Nautical Almanac includes in its front matter), try comparing the times for the moon's lower transit to LAN (bottom right-hand corner of the right page of the Nautical Almanac).  If the moon's lower transit is after LAN, use the east limb; use the west limb if lower transit is before LAN.  Worst case scenario:  you'll need to look at the difference in GHA between the sun and the moon (if the sun's GHA minus the moon's GHA is less than 180°, use the western limb).

    You might want to throw some shades in front of the full moon to get it to about the same brightness as what you're comparing it to.

    Personally, I'm looking forward to the end of mosquito season. 

       
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