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    Re: typical standard deviation?
    From: Jeremy C
    Date: 2009 Aug 16, 08:17 EDT
    I'd prefer sometime in June for the gathering since I will be at sea from February to the first week of June.  If I am home I will be there since it is very close to my home.
    PS  The whole point of celnav on USMS training ships is to get the cadets to be able to do HO229 reductions in their sleep so that they can pass their USCG tests, not to actually be able to get worthwhile positions.  Most of the cadets work their sights "backwards" which i don't like in the least, but that's another topic altogether.
    In a message dated 8/15/2009 11:22:05 P.M. Central Asia Standard Tim, frankreed@HistoricalAtlas.com writes:

    Jeremy, you wrote:
    "This might be something to try at the bi-annual gathering at Mystic with lunar distance measurements.  A number of observers with the same sextant taking say 10 observations or so each should be able to come up with some decent data to begin with."

    Speaking of Mystic, I'm looking at late Spring 2010, roughly eight months from now. Anyone have any dates they would like to exclude?

    I've organized three meetings in Mystic where we had planned to have a group of people shoot lunars and compare results. Two of the events had murky weather: high cirrus and some haze so the results were not all that good. But at the first event, back in September 2005, we had eight people shooting lunars and six got excellent results, all within 0.2 minutes of arc of exact. One was off by about 0.5 minutes of arc --not bad, but not as good as the majority. The last had results which differed by over 2 minutes of arc. Several of us tried his sextant and had similarly wild results, so we know that the blame falls squarely on the sextant in that case. And it was a good, name-brand metal sextant. It had no obvious flaws and no evidence of mis-use, which I think goes to show that we really need to test each instrument. You can't judge a sextant by the polish of its frame or the name of the maker.

    And you wrote:
    "Sadly at sea, the only place you will get a fairly large number of observers with sextants is a school ship with the cadet cadre doing their sea projects.  The big problem with this is that they really don't care enough for the most part to try and get accurate sights and are also neophytes so will be all over the place with their observations.  Still, if I ever go out on a training ships as an instructor, i might look at gathering data of that nature for whatever it's worth."

    Right. The fundamental problem here is that the students are not being graded or judged on the accuracy of their sights. They are well aware that it just doesn't matter. In many of the cases that I know of where significant numbers of students are taking celestial sights today, there's no pressure placed on them to do it well and do it accurately. Clearly, it's hard enough to get them to do it at all, so instructors tend not to scold them too much for low accuracy. One way of getting around this problem is to offer a prize for accuracy. You tell the group of students in advance (so that they have time to practice and hone their techniques) that the best sight accuracy will be rewarded with a $100 gift certificate (not to be spent on a GPS receiver!), and then they will all compete.


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