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    Re: V-Correction for Sun? Answer from UKHO...just one more?
    From: John D. Howard
    Date: 2016 Oct 19, 19:07 -0700

    Mark,

    A lot gets lost when talking about v corrections.

    First consider the sun - our clock time is based on it.  Mean time is the average time it takes the earth to go around the sun in 364 days.  In the meantime the earth has rotated around so you see 365 sunrises.  No being smart a** just reminding you that our 24 hour daily time is based on the sun.  If no correction was added or subtracted the sun would always be close to the clock time.  Rember that GHA is sun time.

    No other body is the basis of time.  In other words the moon, planets, stars seem to rotate the earth at some other rate then normal time.  The sun, on average, moves 360 degrees in 24 hours - no other body does.  It is not exact but in any hour of any day of the entire year the difference is tiny and is easly built into the almanac - always accurate to ONE second of time,

    No so for the moon or planets.  They do not travel around the earth ( appear to travel around the earth ) at an even rate.  There is a rough average but on a particular hour the movement may vary a lot from the average - hence the V correction.

    In summary:  any v correction for the sun would be so tiny that it would not change the GHA by even a second of time.  However the moon and planets NEED the v correction to get an accurate GHA.

    Hope this helps.

    John H.

       
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