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From: Fred Hebard (no email)
Date: Sat May 28 2005 - 09:17:21 EDT
First, I think it's great that Alex is getting observations that are
within 0.1' or 0.2' of arc from his known position, and with similar
precision.
I got the same numbers as Alex for his first set of observations, but
for the second set, my calculated altitudes were about 6.6' smaller
than the observed altitudes. The Naval Observatory site agreed with
my calculated altitudes, so I don't know where the error lies.
One would think that adjusting the backlash on the sextant wouldn't
have affected the readings as long as one always approached the final
setting from the same direction.
One psychological explanation may be that Alex finally became
confident enough in his instrument and himself to get good readings.
We do know that it takes a while to become proficient with the
instrument, although this component obviously is difficult or
impossible to measure.
Fred
On May 28, 2005, at 7:23 AM, Alexandre Eremenko wrote:
> I don't really know what exactly they adjusted
> in my SNO in Freiberg but the sextant seems to work OK.
> Here are the first test results.
> It was Sun at low altitude, but if the good weather persists
> I will go out to do star distances this evening.
>
> May 26, index, 7 obs. of the Sun
> On the arc: 31' (standard dev=0.0')
> Off the arc: 32.13' (standard dev=0.1')
> Sum 63.13' (Almanach: 63.2') IC=+0.565, rounded to +0.6'.
>
> May 27, Sun LL art horizon (plate of water), watch -1 sec.
> Coordinates from Internet: 10d08.8'E, 54d19.7'N
> GMT by watch: Sextant reading:
> 5:25:29 36d27.4'
> 5:27:35 37d03.1'
> 5:29:10 37d31.1'
> Aver: 5:27:25 37d00.5'
> Corrected:5:27:24 37d01.1'
> Divided by 2 and LL corr: 18d43.8' (corrected observed alt)
> Computed alt (by hand w Casio): 18d43.8'. Error: 0.0'
>
> May 27, Sun LL art horizon (plate of sunflower oil), watch -1 sec.
> IC=+0.6. Same place.
> GMT by watch: Sextant reading:
> 6:15:07 51d01.3'
> 6:17:16 51d39.3'
> 6:18:30 52d00.8'
> 6:21:00 52d44.0'
> Averages: 6:17:58 51d51.35'
> Corrected:6:17:57 51d52'
> Divided by 2 and LL corr: 26d10' (corrected observed alt)
> Computed alt (by hand w Casio): 26d09.96'. Error: 0.0'
>
> The certificate for these angles reads:
> 30 40 50 60
> +10" +6" -1" +4"
> and I did not make the corresponding correction,
> because they would not influence the result anyway.
>
> Alex.
>
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