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    Re: Longitude by Sunset
    From: Marcel Tschudin
    Date: 2012 May 7, 02:27 +0300
    Gary,

    Yes, the distance to the horizon is important. I was not high up in the sky, only about 20 m above sea level.

    Marcel


    On Sun, May 6, 2012 at 9:46 PM, Gary LaPook <garylapook---.net> wrote:
    I was ferrying a Cessna 172 across the Atlantic, I was in the middle of the ocean in the middle of the night, it was dark. Suddenly I saw an orange light that got brighter and brighter. "What  the..?"  After a while I realized that it was the moon rising and it was bright orange due to atmospheric effects. From my altitude the horizon was more than 130 NM away so it is always indistinct so I doubt that I first saw the moon just as it cleared the actual horizon.
    gl


    --- On Sun, 5/6/12, Marcel Tschudin <marcel.e.tschudin---.com> wrote:

    From: Marcel Tschudin <marcel.e.tschudin---.com>
    Subject: [NavList] Re: Longitude by Sunset
    To: NavList@fer3.com
    Date: Sunday, May 6, 2012, 8:23 AM


    Alex,

    These few observations were at night. The (full) moon just gradually faded out when approaching the horizon. Like a lamp when you slowly turn the dimmer. My observations could however be related to pollution. I'm still interested to know better under which conditions a moon set (or rise) is actually visible. Yes the visibility of the horizon at night is a problem; one possibly could not recognise that an object sets behind a thin cloud layer slightly above the horizon. There happen to be very often some clouds. From the time the moon completely dimmed away its altitude was calculated to be above the horizon. Also, in case of setting behind something one would notice that part of the shape would be hidden. This was different. You just have a blotch of light which gradually disappears.

    Marcel



    On Sun, May 6, 2012 at 5:06 PM, Alexandre E Eremenko <eremenko---.edu> wrote:

    Marcel,


    In some NavList contributions during February 2010 on "Seeing Moon rising
    an setting ?" I questioned whether it would generally be possible to see
    the moon actually setting (or rising). The extinction of the atmosphere
    close to the horizon was at least during my (few) observations too strong.

    You probably mean in daytime... How about night?
    I understand that horizon will be invisible, but the moment of disapearance of the Moon at night should be clearly detectable, ?

    Alex.






       
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