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Aug 05, 2009


Dear Jeremy,


Subject to double checking my computation - which I have not done yet - and 
working through your example, and assuming that "0.8 arc minute on the arc" 
means :" from instrument value uncorrected for error, substract 0.8 arc 
minute to get such value corrected for error ", I would suggest the following 
results, with TT-UT = 66.0 Seconds of time :


UT of Moon Culmination as seen from moving observer : 9h51m42,6s

Diffrence between Culmination and Transit times : 2s8 . The observer has a 
definite speed towards south ( 13.16 kts south speed component), but - 
interestingly enough - the moon has a declination decreasing by almost the 
same value, as its declination goes 12.85 '/hour towards the south. Therefore 
it explains why both effects almost cancel each other out. This is why both 
Culmination and Observer's True Meridian transit are so close, by only 2.8 
seconds of time.

UT of Moon transit observer's Meridian (i.e. Moon passing due south of moving 
observer) : GMT 9h51m39s8, or LT = 18h51m39s8

Position at time of Moon Transit trough crossing observer's meridian :
N2149.5E13003.7 (sorry I am using Air Navigation Computers notation, since I 
am an Airline Pilot, which means : 21�49'5 N , and 130�03'7 E )

SDEV of measures is 0.6 NM, which gives a Latitude error of 1.0 NM with 2 
sigma and a longitude error of 3'8 with 2 Sigmas.

At 09:00 UT (18:00 LT) , DR position was  N2200.8E13006.5 as reckoned from the 
09h51m39s8 observed Moon fix

At 10:00 UT (19:00 LT) position was N2147.7E13003.2 DR, same as above

At 11:00 UT (20:00 LT) position was N2134.5E13000.0 DR, same as above.

LAST POINT : If I have made Instrument corrections the wrong way, then I need 
to rework your example with instrument corrected values higher by 1'.6 than 
the one I have used. As a consequence, with the assumption that this 1'.6 
angle change should/will have no significant effect on both Parallax values 
and Refraction values as well, then Observed Latitudes will be 1'6 to the 
south and Observed Longitudes are unchanged by reference to indicated 
positions hereabove.


Just be so kind as to confirm me that I have done Instrument error removal in 
the right direction. I somewhat unfamiliar with the terms "ON the Arc" and 
"OFF the arc".

Thanking you for your Kind Attention and Awaiting your reply, I am remaining,


Most Sincerely Yours


Antoine M. Cou�tte


One last question : With such a Height of eye .... where have you been 
observing from ? an Aircraft Carrier upper deck ? (e.g; USS John F. Kennedy 
114 ft !!! )
----------------------------------------------------
[Sent from archive by: antoine.m.couette-AT-club.fr]


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