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    Re: Longitude by Sunset
    From: Marcel Tschudin
    Date: 2012 May 7, 01:54 +0300
    @ Alex:
    No, these observations were not related with clouds, at least not where the moon was. I say this because I observed it with great attention. The moon was first clearly visible. A cloud would have suddenly or unevenly changed its brightness. This was not the case. It just got slowly fainter and fainter.

    @ Greg:
    If the island is sufficiently far it will only rise a little above the horizon. You still could could find out whether the moon sets behind the island or whether it disappears before reaching this low altitude.

    @ h.a.c. van Asten:
    I am not sure if I understand what you mean. The parallax is used for converting earth-centered coordinates to topocentric coordinates. When looking at the setting moon one does it as a topocentric observer, yes, where the light of the moon is refracted from the atmosphere. However, if I do not want to measure something the coordinates, parallax and refraction are not relevant. The observed disappearance of the moon was due to atmospheric extinction.


    On Sun, May 6, 2012 at 7:45 PM, Alexandre E Eremenko <eremenko@math.purdue.edu> wrote:


    These few observations were at night. The (full) moon just gradually faded
    out when approaching the horizon.

    Perhaps there were clouds?
    I am trying to recollect, but cannot remember any instance
    that I've seen a moonset over the sea:-(

    I'm still
    interested to know better under which conditions a moon set

    Me too.


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