# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Multi-Moon line exercise in 2 parts
From: UNK
Date: 2009 Aug 5, 10:30 -0700

```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".

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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