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    Re: Time of Sun & Moon rise and set
    From: Brad Morris
    Date: 2016 Feb 4, 17:31 -0500

    Hello Steve

    There are two meridian transits available at high latitudes.  They are termed the upper and lower meridian transit. 

    The upper meridian transit corresponds directly to the meridian you are on.  The lower meridian transit corresponds to a meridian 180° away from the meridian you are on. 

    There is a singularity directly on the poles since you are simultaneously on all meridians at the same time!  So just arbitrarily pick one.  The nominal time zone in polar navigation is GMT (Dutton, para 4213).

    Your specific question was do we adjust the time of meridian crossing as a function of latitude, specifically at higher latitudes.  Both of the other respondents are correct.  You do not. 

    You are correct that we must adjust the time of rise and set as a function of latitude.  Consider, in high latitudes the sun may never rise or set in a 24 hour period.  Stars at high declination never rise or set when observed from high latitudes.  Yet the opposite is true at the equator, where all bodies rise and set on a roughly 12 hour cycle.


    On Feb 4, 2016 1:34 PM, "Steve E. Bryant" <NoReply_Bryant@fer3.com> wrote:

    Dear NavListers,

    For purposes of determining time of sun rise and set, I understand it is important for adjust time according to your latitude (and of course longitude); but, is it necessary to make adjustments based upon latitude when determining meridian transit?  I suspect not; nevertheless I ask the question particularly with respect to the extremes as you approach the poles.

    Steve Bryant


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