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    Re: Scrap paper with time sights c.1870
    From: Lars Bergman
    Date: 2013 Feb 26, 05:41 -0800

    I have made some further research into the “scrap paper” voyage presented by Frank. In the enclosed excel file is my final (I hope) summary. I am quite sure the voyage was made 1855-1856, or at least the NAs for those years were used. The voyage itself can of course have been made later. Can anyone find another period of time with as good match as this?

    General observations:
    The equation of time is always interpolated to the time of observation, but for the chronometer correction the same value is used during the day, although it changes by 1s every five hours.
    The altitude corrections show just a few irregularities, indicating that index error seems to be stable. A 4’ correction for index error and dip seems to be most usual.

    Some comments on some specific observations:
    Obs no 1: Log sec latitude is overwritten, but the original value of 09632 is used in the calculation. Maybe the navigator intended to change the values to those of observation 2, but realized this would become too messy.

    Obs no 2: The uncorrected sextant altitude is mistakenly used in the calculation of the remainder, thus its log sine is in error. Also some non-easily-detected changes and errors in the chronometer correction gives a longitude error of 2’.

    Obs no 8: Here the ignorance to interpolate the final log to correct LAT introduces a 3s error, resulting in a 1’ longitude error.

    Obs no 12: The correct LMT of 3h53m29s is mistakenly stated as 3h53m39s in the longitude calculation, resulting in a 3’ longitude error.

    Obs no 16: Similar error as in obs 12 resulting in a 1’ long error.

    Obs no 18: Log sine remainder is taken out for 67°35’ instead of 67°34’, giving a 1s error in LAT. Cannot read the resulting longitude, but it should be 15m57s with the values given. Sometimes I think the written value is 18m, and if this really is the case this could perhaps explain that a second am observation, no 19, was made less than an hour later.

    Obs no 19: The final longitude calculation is missing but should have been 15m10s with the values given. The EoT is obviously wrong but makes no significant difference in the result.

    I don't think that much more information can be squeezed out of that paper.

    Lars
    59N 18E
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    File: 122488.summary-1855-1856.xlsx
       
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