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    Re: Extremely poor conditions??
    From: Greg Rudzinski
    Date: 2012 Mar 21, 12:58 -0700

    Alex,

    I have had two different digital atomic clocks jump a complete minute on me out of the blue for no reason. For this reason the setting of a quartz watch is done by shortwave radio. GPS time should be good but if the atomic watch is jumping a minute it will jump the time right after the correct time is entered.

    I still think you are a minute out in your time rather than having a horizon 3.5 miles away elevated 11 moa.

    You will need to go back out to the lake to take more observations using the GPS time directly from the GPS unit or a shortwave time tick directly. Also break out the artificial horizon for a set of observations to compare. I would be interested in these results if you or Bill can duplicate the warm air over cold water conditions.

    Greg Rudzinski

    --- On Tue, 3/20/12, Alexandre E Eremenko <eremenko---.edu> wrote:

    > From: Alexandre E Eremenko <eremenko---.edu>
    > Subject: Re: Extremely poor conditions??
    > To: "Greg Rudzinski" <gregrudzinski---.com>
    > Date: Tuesday, March 20, 2012, 6:44 PM
    >
    > Greg,
    >
    > > What type of watch are you using ? Sometimes with
    > analog wrist watches it is
    > > easy to get the minute hand set in between minutes so
    > that an even one
    > > minute error in timing is marked. If you marked time
    > one minute later then
    > > all your errors would be eliminated.
    >
    > I am aware of this possibility (because I like analog
    > watches:-)
    > In this particular case, however we used Bill's digital
    > watch with large
    > display which
    > is absolutely accurate (receives radio signals from an
    > atomic clock).
    > But even this watch we compared with GPS. The difference was
    > less than 1
    > second.
    >
    > In most observations one of us served as an assistant, that
    > is one person
    > measured the altitude and another recorded the time. Only in
    > one
    > of the series, with TS I used my analog watch.
    >
    > So the errors cannot be explained by watch. The only
    > possible
    > explanation seems to be some very strange refraction as
    > Frank suggests.
    >
    > Alex.
    >
    > >
    > > I have your (Hs) Sun lower limb at 24* 10' for your UT
    > 21:34:00 3/17/2012
    > > getting an intercept of 11' away
    > >
    > > If UT is 21:35:00 the intercept is zero.
    > >
    > > If electronic sight reduction was used then sometimes
    > the day gets entered
    > > off by one. For 3/16/2012 the intercept is 4' toward.
    > >
    > > All of these types of mistakes should be suspected
    > before blaming the dip
    > > correction value.
    > >
    > > Greg Rudzinski
    > >
    > > [NavList] Extremely poor conditions??
    > > From: Alexandre Eremenko
    > > Date: 19 Mar 2012 17:58
    > > Here I post a series of observations that puzzles me
    > very much.
    > > On March 17, in an unusually warm weather for this
    > season, we spent an
    > > afternoon with Bill Burchell in St. Joseph harbor on
    > lake Michigan,
    > > N 42d06'8, W 86d29'5, with his Astra sextant and my TS
    > (pocket sextant).
    > > We made 7 series of 3-5 observations each of Sun and
    > Venus altitudes over
    > > the lake
    > > from a jetty, approximate height of the eye 12 ft.
    > >
    > > The weather was sunny and warm (80 degrees F by Bill's
    > thermometer).
    > > The horizon looked very sharp, though there was a lot
    > of glare under the
    > > Sun.
    > > We took a great care in determination of the Index
    > error (from the Sun, from
    > > the horizon and from a remote roof), in the beginning
    > and in the middle of
    > > observations. Our determinations varied between 0 and
    > 0'.5, but most were
    > > less than 0'2.
    > > Astra had a perceptible side error (about 1/5 of the
    > Sun SD).
    > > In the following
    > > I do not correct for the Index or side error.
    > >
    > > My TS has zero Index error to the best of
    > > my knowledge. I had excellent results with this pocket
    > sextant which I
    > > posted on the list in the past.
    > > We observed Sun (lower limb) and Venus altitudes,
    > corrected for
    > > the height of the eye, semidiameter and refraction, and
    > compared the results
    > > with computed altitudes.
    > > By the "error" I mean the observed and corrected
    > altitude minus the computed
    > > altitude.
    > >
    > > GMT 21:34, Astra, Sun. Errors: -11'5, -14'2, -9'9,
    > -9'2, -6'3
    > > (Aver.-10.2,SD=2.6)
    > > GMT 21:46, Asrra, Sun. Errors: -9'9, -10'5, -10'6,
    > -10'5, -10'5 (Bill)
    > > (Aver.-10.4,SD=0'25)
    > > GMT 21:54, Astra, Sun. Errors: -11'1, -12'2, -8'7
    > > (Aver.-10.66,SD=1'5)
    > > GMT 22:38, Astra, Sun. Errors: -11'4, -8'4, -9'7,
    > -10'5, -9'5, -10'3
    > > (Aver.-10.0, SD=0'9)
    > > GMT 23:46, Astra, Venus. Errors: -9'7, -10'0, -9'4,
    > -12'3, -11'4
    > > (Aver.=-10.6, SD=1.1)
    > > Sun set in the middle of this observation.
    > > GMT 23:58, Astra, Venus. Errors: -6'3
    > >
    > > Now pocket sextant observations (w/o telescope)
    > > GMT 22:14, TS, Sun. Errors: -11.3, -13.8, -10.8, -13.7,
    > -13.4
    > > (Aver.=-12.6, SD=1'3)
    > > GMT 00:03 (March 18) TS, Venus. Errors: -11'0, -9'8,
    > -7'8.
    > >
    > > Can anyone propose any plausible explanation of these
    > enormous NEGATIVE
    > > systematic errors? I never had anything of this
    > magnitude before.
    > > And as you see, they are pretty stable, about 10-11
    > minutes.
    > > I understand there can be a dark strip on the water,
    > mistaken for the
    > > horizon. But this will lead to POSITIVE errors
    > (overshots). Refraction which
    > > DECREASES the apparent altitude???
    > > We are talking of the errors about 1/3 of the diameter
    > of the Sun!
    > > What could possibly cause this?
    > >
    > > Alex.
    > > P.S. Bill promises to find the water temperature of
    > water on this day,
    > > but it is really
    > > hard to believe in this kind of abnormal refraction.
    > >
    > >
    > >
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