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    Re: Silicon 84
    From: George Huxtable
    Date: 2002 Oct 19, 15:02 +0100

    Mike Burkes said, inter alia:
     When shooting Polaris I noticed or inferred from navigation texts that
    averaging several shots is not mentioned. On occasions I have experienced
    increasing altitudes in the course of a Polaris session. Any feedback would
    be appreciated and thanks much!
    Polaris is not at the the pole but a "large" fraction of a degree away, so
    its altitude does vary. But not by more than about 12 arc-minutes in an
    hour, at its greatest, increasing, or decreasing. In addition, any
    Northward or Southward component of ship's velocity would provide an
    additional change of Polaris altitude of, say, 7 arc-minutes per hour, if
    the speed of the vessel were 7 knots. Even if these were to add, this would
    cause Polaris altitude to change by only 19 arc-minutes per hour, or 1 arc
    minute in about 3 minutes of time. This slowly changing altitude would not
    be very obvious to an observer unless the series of measurements was rather
    prolonged. So how long was the "Polaris session" that Mike refers to, and
    how much "increasing altitude" did he see? And what was the speed of his
    George Huxtable
    George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    Tel. 01865 820222 or (int.) +44 1865 820222.

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