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Subject: Re: Data from three lunars, with some comments
From: Dan Allen (danallen46@XXX.XXX)
Date: Tue Jan 14 2003 - 17:07:07 EST
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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