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    Re: Very Small Altitude-Accurate Results
    From: Bruce J. Pennino
    Date: 2015 Aug 15, 14:48 -0600
    Hello:

    I recorded some low angle setting sun data yesterday evening.  Here is all pertinent info , and if I leave something out , let me know.  The data were  recorded Friday  8/14/2015 at 41d 56.7'N, 70d 0.4.6 W. The beach is called "Duck Harbor", Wellfleet, Massachusetts, USA, Cape Cod. Sighted sun LL, watch is fast 3 seconds,IC equals zero, HoE 11 ft. Weather was pleasant , good horizon,temp about 80 F, press about 29.9"Hg.

    Times are uncorrected Eastern Standard USA. Data: 18:25: 51  2d 08.2'; 18:27:14  1d 52.8'; 18:28:24  1d 42.6'; 18:29:35  1d 31.0'   end.    As someone once said......" Very Interesting".  Have a good day.

    Bruce

    -----------------------------------------

    From: "Stan K"
    To:
    Cc:
    Sent: 11 Aug 2015 17:52:00 -0700
    Subject: [NavList] Re: Very Small Altitude-Accurate Results

    Related to this subject, it should be noted that the Nautical Almanac changed its refraction corrections in 2004.  Apparently an oversight, the refraction formula on page 280 did not change until 2005.  The difference is only significant for altitudes less than 2º, but the change affected the critical values of apparent altitude on the Altitude Correction Table 10º-90º - Sun, Stars, Planets (Table A2).

    The new formula on page 280 does not always agree with the new Table A2, as the old formula did not always agree with the old Table A2.  If they changed the critical values of feet to make it agree, it would not agree with the critical values of meters, and vice versa.  But, practically speaking, either formula is close enough.  Other factors come into play in "real life" anyway, such as anomalous refraction.

    Stan





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