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    Re: stange results from AM and PM sun shots
    From: Bill B
    Date: 2012 Sep 27, 19:54 -0400

    On 9/27/2012 12:47 PM, Alan S wrote:
    > I wonder is the above mentioned in just a peculiarity of late Sept. when
    > Sun's declination is so small, in some instances, less than 1D South.
    > Any ideas or light to be shed.
    
    Alan
    
    Keep in mind that what you see is not what you get.  We are told with 0d
    declination the sun will rise and set due east and due west,and night
    and day will be equal lengths. This is not true for three reasons.
    
    1. If the declination was 0d at LAN in September, the declination would
    be N at sunrise and S at sunset.
    
    2.Even if declination was 0d at rise and set, that would be for the
    center of the sun, not the upper limb which we use to define rise and set.
    
    3. Due to refraction, we are seeing a limb that is not there in a
    vacuum. The refraction correction would be -0d 33!8 for the center of
    the sun or upper limb on the horizon. Therefore it is quite possible to
    have an Hc north of 90d or 270d near the autumnal equinox.  If memory
    serves there is about an 8 day lag past the equinox before light and
    dark are equal.
    
    To make matters more confusing, 0d declination does not exactly define
    the equinox as I recall. Somewhere in my archives there is an
    explanation and diagram posted by a list member perhaps 7 years ago.
    I'll try to locate locate that.
    
    In memory of George I'll mention that when I learned the above I was as
    disillusioned as a kid finding out his "sea monkeys" were nothing but
    brine shrimp. This caused George to rebuff me as he asserted younger and
    foreign list members had no idea what I was talking about. To get those
    not in the know up to speed:
    http://en.wikipedia.org/wiki/Sea-Monkeys
    
    Bill B
    
    
    
    
    

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