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    Easy compass check
    From: Bruce J. Pennino
    Date: 2015 Mar 19, 09:17 -0700


    I keep a hand held compass with my sextant and check the compass every once in a while.  Of course the hand held compass is a great teaching tool.  I've found that it helps students bring earth tilt, declination, local magnetic variation all together. But, tomorrow at sunrise and sunset we have the easiest day of the year to check your hand compass (boat compass somewhat more work). At spring and fall equinox the sun rises  due east (true) and sets due west (true), declination  of sun  zero. Where ever you are,  determine from a chart your local magnetic variation, keep the compass away from your big belt buckle, auto and transmission towers, and measure the magnetic bearing at sunrise or sunset.  Check the compass reading with the expected reading (knowing the  local variation).  Error should be a couple of degrees at most. If you do the measurement up to an hour before sunset, or an hour after sunrise, Eldridge tells me  that the bearing increases to the south about  1 degree every six minutes up to 10 degrees at one hour after sunrise.  At the end of the day , the bearing is smaller and changes at the same rate.  On your compass, first hint of sunrise at 90 degrees true, last glimmer sunset 270 degrees west, plus or minus local variation.  This New England winter ( west of Boston) is starting to affect me, maybe more snow this weekend, and still really cold.  Spring is really a big deal around here....it will eventually really arrive....another month or so.

    Best regards   to all.



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