NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lat and Long by moon transit.
From: Peter Hakel
Date: 2011 Jan 30, 13:33 -0800
From: Hewitt Schlereth <hhew36@gmail.com>
To: NavList@fer3.com
Sent: Sat, January 29, 2011 8:33:22 AM
Subject: [NavList] Re: Lat and Long by moon transit.
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
From: Peter Hakel
Date: 2011 Jan 30, 13:33 -0800
I start with the summary of the results for UT=10:00:00
Jeremy's GPS:
Lat: N 21d 48.7'
Lon: E 130d 07.5'
Kermit's result:
Lat: 21d 47.6'
Lon: E 130d 03.2'
Hewitt's result:
Lat: N 21d 47.1'
Lon: E 130d 03.5'
To which I add:
Lat: N 21d 47.2'
Lon: E 130d 05.2'
The final step was the -95s DR shift from the moment of the last observation (for which I calculate the position, see attached) to UT=10:00:00.
My thanks to Jeremy, Kermit, and Hewitt!
Peter Hakel
Jeremy's GPS:
Lat: N 21d 48.7'
Lon: E 130d 07.5'
Kermit's result:
Lat: 21d 47.6'
Lon: E 130d 03.2'
Hewitt's result:
Lat: N 21d 47.1'
Lon: E 130d 03.5'
To which I add:
Lat: N 21d 47.2'
Lon: E 130d 05.2'
The final step was the -95s DR shift from the moment of the last observation (for which I calculate the position, see attached) to UT=10:00:00.
My thanks to Jeremy, Kermit, and Hewitt!
Peter Hakel
From: Hewitt Schlereth <hhew36@gmail.com>
To: NavList@fer3.com
Sent: Sat, January 29, 2011 8:33:22 AM
Subject: [NavList] Re: Lat and Long by moon transit.
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
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