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On Tuesday, January 14, 2003, at 11:55 AM, Fred Hebard wrote:

> I checked the 12/27/02 data (and the others) by plotting the observed
> distance against the time of observation.  I was stunned and
> delighted by how well the data fit a straight line (and one expects
> this line to be straight over short intervals), with an R^2 of better
> than 0.997.  I then picked the best observation, one that was most
> centered on the regression line, and used that to compute time with
> Bruce Stark's tables.  This was the 6:31:17 observation.  The time
> came in at about 12 seconds behind UT1.
>
> These data convinced me that my newly purchased Husun sextant was
> worth repairing rather than reselling (the handle was burst apart by
> leaking batteries), and encouraged me to explore further.  But I'm
> not so sure I would have felt that way if the data had been from the
> 1/8/03 or 1/11/03 sights.

Thank you for sharing your lunars with us.  I have got to get out and
start taking lunars myself one of these days.  I am still struggling to
understand the computations myself.

Your experience is like my land sights: some are amazingly accurate
while
others are not.  We know this because we have the luxury of comparing
our
sextant results with an averaged GPS location or a typographic map
location.

But how would we do without these crutches?  How would we do on a
rolling
ship in a storm?  What statistical measures or rules of thumb can be
used
to help throw out the bad sights and keep the good ones?  This is an
area
that I am considering more and more.

Dan

   

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