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    Re: Mars - Mercury Question
    From: Don Seltzer
    Date: 2013 Feb 7, 12:43 -0800

    Frank wrote: Yes, but not "practicable" ...

    And the terms of the Longitude Prize also stipulated 'useful at sea'. That was the failing of the Jovian Moon method - in principle it was accurate enough and occurred frequently enough to be useful for points on shore, but it was not possible to keep a telescope pointed continuously at Jupiter for an accurate timing while aboard a ship at sea.

    Even despite the best efforts of Dr Maskelyne and Capt Aubrey, RN to invent a gimballed chair for counteracting a ship's motions.

    Don Seltzer

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