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    What is the radius of the Prime Vertical?
    From: David Pike
    Date: 2019 Mar 14, 10:08 -0700

    It doesn’t do to be too inquisitive.  I couldn’t help wondering, if the Prime Vertical is defined as:

    a great circle in the celestial sphere passing through the zenith and the east and west points of the horizon.

    then what is the radius of that great circle?  Is it as big as you want it to be, or is it the radius of the celestial sphere?  If so, then what is that?  Is it infinite?  Wikipedia is of little help for once, because if asked what the radius of the prime vertical is, it assumes you want the radius of curvature of the Earth between two points E-W of each other.  DaveP  

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