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On Tue Dec 14 2004 - 18:31:47 EST Ken Muldrew wrote:

>I wonder if his DR
>put him out?
>Comparing his calculated altitudes to those given by the USNO
>celestial navigation data site, Thompson has
>Aldebaran too high by 2 degrees and Altair too low by 2 degrees.

This explanation is plausible.
According to the formula by Frank Reed, see, for example, my message of
Tue Nov 02 2004 - 12:43:15 EST)
The error in the cleared lunar (ErDist) which is due to the error
in star's altitude (ErStarAlt) is approximately given
by the formula:
ErDist=0.016csc(dist)cos(StarAlt)(ErStarAlt)
With Thompson data for Altair and Aldebaran (Nov 26, 1800)
assuming ErStarAlt=2 deg, we obtain approximately
ErDist=2'
Which implies an error in longitude of the order of one degree.

Why did not he measure altitudes?
Could you also explain the notation: what is TA and what's AA?
And what are the numbers
+3'48", -4', +2"
in Altair part and similar line in Aldebaran part?

Further, Ken wrote:

>perhaps one could work
>backward from his calculated altitudes to get the DR position.

Perhaps. For this we need to know the time
used in his alt calculations, and the equation of time
from his almanac.
I suppose it was 9:03:45 for Altair and 9:12:47
(P. M. ?!) local time.

Alex.

   

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