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    Re: Relative Importance of Accurate Timing of Sight for Lunars versus Altitude Sights
    From: John Kabel
    Date: 2003 Jun 10, 07:29 -0400

    I agree.  When I was studying celestial, I didn't get really good until
    I got the mechanics of timing the sights down pat.  I ended up with my
    watch with its face on the inside of my left wrist.  I would swing the
    sextant and start a chant of "and one and two and three ... " as the
    body touched the horizon.  Then an immediate glance to the watch while
    pressing the sextant light, which illuminated the watch somewhat,
    correcting the observed time for how far I got in my chant.  At that
    point I read and recorded the angle and the time on a log sheet.
    
    When my observation plans matched reality, on a few nights, I got to 50
    s per sight, 45 to 50 or so sights in a row.  The watch would be
    carefully compared with a radio time signal, and I was keeping track of
    its drift day by day, on a chart.  I could predict error fairly
    accurately.  Only once all these pieces came together did I get any
    sights under 0.5 ' at a known land position.  Then I started expanding
    the conditions of sights, to partly cloudy twilight, artificial
    horizons, etc., to build up more practice.
    
    It must have worked, because I passed.  And still enjoy the use of my
    sextant to this day.
    
    Great discussions on the list lately, folks!!
    
    John Kabel
    London, Ontario
    
    > It has taken me a long time to where I can consistently get my altitude
    > sights to under 0.5' of arc from a known position on dry land, often,
    > now, under 0.2' of arc.  A critical component of that has been judging
    > the exact moment of contact and hitting the stop watch accurately at
    > that moment.  After setting the angle, I generally wait for the object
    > to converge with the horizon, or itself in the artificial horizon, and
    > try to hit the stop watch when contact occurs.
    >
    > However, I always had a fair amount of luck with lunars, even before
    > improving my timing technique for altitude sights.  That was back when
    > I would look down at my watch after perfecting the contact and record
    > the time.
    >
    > I still prefer this second method for lunars and believe it is the best
    > for that observation.  That is because 12 seconds of time elapse, more
    > or less, between each shift of 0.1' of arc in a lunar.  It doesn't make
    > much difference whether you're 2-4 seconds out.  It's much more
    > important to get the angle measured to the utmost precision possible
    > than to time the sight accurately.  You need to concentrate much more
    > on proper manipulation of the micrometer than on the time, like when
    > checking index error by determining the semi-diameter of the sun.
    >
    > Any comments?
    
    
    

       
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