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

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Re: Lat and Long by moon transit.
From: Hewitt Schlereth
Date: 2011 Jan 29, 12:33 -0400
Hi Antoine -

To figure the latitude, I took Jeremy's highest Hs at 09-50-00 of  55° 27.5' and came up with  21° 45.0' N. Moving this to account for his ship's movement, gave me 21' 47.1' N at 1000.  (21° 48.7 N = GPS at 1000 GMT). So, I have him 1.6' south of the GPS. (You have him at 21° 47.6' N).

Since the altitudes were taken very close to meridian passage and were changing only a few tenths/min, I was a little dubious about how my paper-and-pencil method for longitude would turn out.

Anyway, I took the two equal altitudes - 55° 25.6' at 09-48-15 and 09-55-19 - averaged the times, and came up with an uncorrected longitude at 09-51-47 of 130° 02.1 E.  Applying the correction of .7' for ship's net motion of .4 kts directly toward the moon, gave me a longitude of 130° 01.4' E. Accounting for the ship's movement south and west between 0950 and 1000 gave a 1000 longitude of 130° 03.5' E. So, I have him 4.0' of longitude west of the GPS position of 130° 07.5' E. (You have him at 130° 03.2' E).

You and I agree to 0.5' of latitude and 0.8' of longitude.

For some reason your attachment came up scrambled on my Mac (was it doc.x?), so I don't know how this compares with others' results.

Best regards.  Hewitt

On Sat, Jan 29, 2011 at 4:19 AM, Antoine Couette wrote:

RE :
http://www.fer3.com/arc/m2.aspx?i=115506
[NavList] Re: Lat and Long by moon transit.
From: hhew36---com
Date: 28 Jan 2011 20:27

IT DID IT AGAIN : THIRD and LAST attempt since some text by the end of my post got suppressed on first two trials. This time, I have slightly modified the arrangement of the end of my text, and did not include the Annex which was transmitted OK on the first 2 trials. Will it go thru entirely this time ???

Kermit

*******

Dear Hewitt,

You wrote : "Looking at Kermit's results, I'd say he used the 6-30-2009 date."

YES ! I used the 6-30-2009 (UT) date, with LT-UT = +9 , which was subsequently confirmed as correct by Jeremy.

And for the time of the Moon Transit (UT=09h51m39.7s), I am getting the following data for the Moon :

GHA = 229°56'3 with RA hourly change = +0°.5064 and

DEC = S-12°38'7 with DEC hourly change = -12'.86

The actual Moon declination on 6-30-2009 was (much) further to the South than what Jeremy first indicated : QUOTE The declination is about 7 degrees south UNQUOTE, which tells us that Jeremy's clue would actually have been more appropriate for 6-29-2009 as you say, but it was nevertheless quite "valid" for 6-30-2009 in the sense that the Moon was - for both dates - South of the 6-30-2009 Observer's Position.

Hewitt, since in your subsequent post (RE : http://www.fer3.com/arc/m2.aspx?i=115508) you indicated : QUOTE Thanks, Jeremy,, that clears it up nicely, -Hewitt UNQUOTE, which results are you getting for this Moon LAN ?

I would guess that all of us - yourself, Peter, Andres, Kermit, and others - should derive (almost) the same end result (see my enclosed listing of entries and results : NOT INCLUDED IN THIS THIRD SENDING TRIAL), even with a plain parabolic fit to Jeremy's data which certainly should be fully appropriate here given both the "moderate" (55 degree) Culmination height and the rather "tight" (+/- 12 minutes of time) time-span around Culmination Time in this specific example.

Best Regards

Kermit

Antoine M. "Kermit" Couëtte

LAST NOTE TO THE ATTENTION OF FRANK E. REED : Now and then, I have noticed that some of my posts get "shortened/abridged" by your NavList Computer system. Any clue or reason for that, Frank ?

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