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    Re: Learning celestial navigation
    From: Lu Abel
    Date: 2017 Mar 17, 20:52 +0000
    I'm not sure I agree with "at least three nautical miles"  One can always do a "dip short" sight where the water ends before a natural horizon is reached.   (The distance to the horizon in nautical miles is 8/7 time the square root of the HE [height of eye above the water])  If you're near the water's edge, the horizon is indeed about 3 miles away.  If you're standing on the top of a cliff, it's further. 

    As a sight checker for the US Power Squadrons' celestial courses, I've checked many dip-short sights.

    Stan Klein's wonderful Celestial Tools software includes dip short calculations/corrections if you want to see an example.

    From: Bob Goethe <NoReply_Goethe@fer3.com>
    To: luabel@ymail.com
    Sent: Friday, March 17, 2017 12:15 PM
    Subject: [NavList] Re: Learning celestial navigation

    Generally speaking, what Alexandre says about the importance of being near the sea is true.  If you have a beach to stand on that looks west, for instance, you can take sights anytime in the afternoon.  You cannot beat this for giving you long windows of opportunity for practice.
    However, if you have a lake nearby where you can get a view of the sun with at least 3 nautical miles of water between you and the shore underneath the sun, you can take sights there.  The lake near my house (see attachment) is shaped such that from my observation point, in the summer I have 2 or 3 hours every day where I can take sextant sights over the lake and get valid data to use in fixing my location.
    Further, as somebody else has indicated, when you look for a textbook to guide you in your learning process, glance through it before you buy it to ensure that you see the words "artificial horizon" someplace.  You want a textbook that will guide you through the process of taking sights using a bowl of water or molasses  as an artificial horizon, in addition to the more conventional sights over a distant horizon.

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