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    Lunars on a whaling voyage: 1847-1850
    From: Frank Reed
    Date: 2009 Sep 2, 15:20 -0700

    Here's some longitude data from a whaling voyage in the late 1840s. This is 
    from a logbook that I am still working on so I don't want give complete 
    details on the ship involved at this time. See what you can make of these 
    data points...
    These are all the cases of longitude by lunars in this particular logbook. 
    This is very late in the history of lunars so they are used only as an 
    occasional check on the chronomter. "Lon C" indicates longitude by 
    chronometer. "Lon L" is longitude by lunar (these are the way they were noted 
    in the logbook incidentally). I include the latitude in case you want to 
    convert longitude minutes to nautical miles. The vessel leaves Connecticut in 
    late 1847. The first recorded lunar observations are taken after crossing the 
    Dec 11, 1847: Lon C: 29.02.45W, Lon L: 29.28.45W, Lat:  5.24.47S
    Dec 12, 1847: Lon C: 30.30.00W, Lon L: 31.11.00W, Lat:  7.28.37S
    On December 15, 1847, the logbook says:
    "Long by Lunar Observations 34.34.15W by it I regulate my Chronometer by 
    adding 4'38" & ---- 3&2/3 seconds per day" (the word indicated by "----" is 
    illegible but appears to be "losing" with "gaining" written over it).
    Dec 31, 1847: Lon C:  49.36.30W, Lon L:  49.20.45W, Lat: 37.22.24S
    Feb 26, 1848: Lon C:  88.40.15W, Lon L:  88.28.30W, Lat: 22.52.43S
    Feb 27, 1848: Lon C:  89.35.45W, Lon L:  89.39.00W, Lat: 21.53.00S
    Feb 28, 1848: Lon C:  90.49.15W, Lon L:  90.51.00W, Lat: 20.34.40S
    Mar 25, 1848: Lon C: 144.05.30W, Lon L: 144.07.00W, Lat: 18.22.15N
    Apr 23, 1848: Lon C: 149.04.15E, Lon L: 149.00.00E, Lat: 25.10.22N
    Apr 25, 1848: Lon C: 148.25.15E, Lon L: 148.38.15E, Lat: 27.32.37N
    From May through September they are whaling in the Sea of Okhotsk often in 
    sight of land. The vessel's position is recorded nearly every day though 
    sometimes the  positions are labeled "about". There is only one recorded 
    longitude by lunar in this period:
    Jul 24, 1848: Lon C: 152.18.15E, Lon L: 152.16.00E, Lat: 55.52.27N
    After October 1 or so, they are bound for Hawaii.
    Oct 19, 1848: Lon C: 165.59.11E, Lon L: 166.32.00E, Lat: 35.24.20N
    Oct 31, 1848: Lon C: 154.40.45E, Lon L: 155.20.45E, Lat: 26.56.37N
    From November 5, 1848 through about December 13 they are at Maui (spelled 
    Mowee). One lunar on the voyage from Hawaii to Guam:
    Jan  1, 1849: Lon C: 160.33.15E, Lon L: 160.54.00E, Lat: 13.12.10N
    They spent most of January at Guam where they witnessed a major earthquake and 
    a tsunami on January 24, 1849 noting that the "ground sank about 12 feet at 
    the head of the bay". From February through early August they were whaling in 
    the Sea of Japan frequently in sight of land. As in the Sea of Okhotsk, the 
    position is noted daily but there is little doubt about the longitude since 
    they see land often. After about August 12 they are "Homeward Bound" with a 
    stop in Hawaii (Sep 30 - Oct 17).
    Sep 10, 1849: Lon C: 163.01.30W, Lon L: 162.54.30W, Lat: 38.29.06N
    Nov  5, 1849: Lon C: 158.27.45W, Lon L: 158.26.30W, Lat:  7.57.34S
    Mar  7, 1850: Lon C:  68.15.00W, Lon L:  68.35.00W, Lat: 28.57.00N
    Two weeks later they sight land and return home to Connecticut arriving in a "thick snow storm". 
    The use of lunars in this voyage is typical of the late 1840s in my experience 
    with logbooks. After this date, lunars rapidly disappear from the logbooks 
    (though of course there were exceptions). By the way, I am not sure that the 
    exact dates are correct (plus or minus one day is possible). I haven't yet 
    determined how the "dateline" is handled in these logbook entries, and I 
    don't recall whether he was using "sea days" in the reckoning.
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