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A while ago I posted a technique to use the Noon sight to obtain a
"passable" estimate of both Lat. and Long.Some fellow list members replied
in horror and disbelief that I would post this.Only 1 other listmember
stated that a well managed Noon sight could be used to obtain more than an
estimated Lat.
While at sea for the last weeks I had time to attempt to take actual sights
and reductions of the Noon sights and present the data from these sights to
the list.We proceeded from Pt. Furmin T.S.S. to an area in the Pacific to
drop bouys,take data and retreive the bouys.
This is mainly a mechanical proceedure and with practice is not that
diffacult to acheive.Care must be taken in the timeing of the sight or the
errors can give results that are grossly differant from the actual position.
There are 2 keys in the proceedure to accomplish this.Being ready at the
calculated time to take and record the cut and correct calculation of the
1st and 2nd approximation of the EP.The takeing of the cut at the correct
time is all mechanical and the more one does it the better one becomes at
it.The accuracy of the calculated EPs to the actual positions is largely
reliant on how close one keeps the vessel to the trackline.On the bigger
vessels the helmsman has standing orders to head the vessel in a momentary
direction(overriding the auto-steering)to keep the vessel within a certain
distance of the trackline.This assures the Ep and position of the vessel are
close.
The Lat. and Long. were reduced.Plotting sheets were used and the ship's GPS
position was used only to compare the closeness or distance of the reduced
positions.
Constants for all sights : Ie=-0.1'.ht.=28 ft.Sun's L.L. used on all
sights.EP used as the AP for the sights
Depart 33* 20.0'N, 118*05.0"W, 0737, 1-15-04.C=209*T, s=15 kt
1st approx. EP 1209 LMT M.P.1-15-04 32*20'30"N,118*44'27"W
1209 lon.=118*44'27"W
n.l. GHA=117*40'12" at 200000 GMT
d GHA= 1*4'15"
d T =     4'17"
cor GMT=200417
zd = + 8 rev.
zt LAN=120417
2nd approx. EP 1204zt  32*21'36"N,118*43'45"W
c.l. lon. = 120* W
1204 lon.=118*43'45"W
d * = 1*16'15"
d T = - 5'5"
LMT 120919
zt LAN=120414 I didn't get the sight taken on time.12 sec. late
LAN temp.=53* F,29.80' Hg,hs =36*21.4',Ho=36*31.3',dec
=21*07.9'S,GHA=118*46'42"
120426 noon pos.=32*20'48"N,118*46'42"W
1204 EP=32*21'36"N,118*43'45"W
1205 gps= 32*19'55"N,118*43'47"W
1-16-04 0325 arrive in test area.Propulsion cut,deploy bouys.collect
data.Ride shotgun on bouys and show lights for RAM
0325 gps= 28*45'6"N,121*04'18"W.    Check gps pos. at 0625=
28*42'54"N,121*09'39"W. drift=240*T,s=1.77 kt.
1st approx. 1210 LMT EP= 28*37'45"N,121*19'27"W
LMT lon.= 121*19'27"W
n.l. GHA= 117*34'54" at 200000 GMT
d GHA= 3*44'33"
d T= 14'58"cor GMT= 201458
zd=  +8 rev.
zt LAN= 121458
2nd approx. EP= 28*37'44"N,121*19'27"W
c.l.lon.= 120*W
1215 lon.= 121*19'27"W
d *=1*19'27"
d T= + 5'18"
LMT= 120940
zt LAN= 121458    I was late again on the sight
LAN temp.=51* F,29.78'Hg,hs=
40*15.4',Ho=40*25.5',dec.=20*56.6'S,GHA=121*19'24"
121459 noon pos.= 28*37'54"N,121*19'24"W
1215 EP= 28*37'44"N,121*19'27"W
1215 gps= 28*37'49"N,121*19'29"W
1-16-04 1438 shot a sun line to combine with noon pos. Clouds starting to
cover sky,winds increasing temp.=48*F,29.78'Hg
1438 EP= 28*35'47"N,121*23'36"W
dec= 20*55.4'S
hs=29*30.1'
Ho= 29*39.6'
Hc=29*39.4'
a= 0.2m T
143812 r-fix pos= 28*35'48"N,121*24.0'W
1438 gps= 28*36'00"N,121*24'07"W
For the next 37 hrs. no sights could be attempted due to cloud
cover.Departed the area 1-19-04 at 1733.I took 1 more noon sight on the 20th
on a north heading giveing similar results between the gps and reduced
positions.Even the 1-15-04 pos when I missed LAN by 12 sec. was less than 5
n.m. from the gps pos.The 16th's LAN  and r-fix pos. had less than 1 n.m.
seperation from the gps pos.The closest land from this area is 133 n.m.
So,I ask,what is so very wrong about showing someone this method?What do you
feel is so difficult in timeing a sight?Even if one's timeing of the noon
sight is off by many secounds one can still get a "passable" fix.If the
conditions after the 16th's noon pos were such that you couldn't get any
LOPs for days after and didn't have gps,software for a trackline or a
reliable auto-pilot it gives one a better idea of where one was then just a
Lat estimation at LAN.Would I depend on this method solely for position
finding approaching land or in congested areas?No.But then again,in todays
world,one doesn't have to depend on CN position finding at all.It's just
another tool to use when needed.There is a seperation from strict theory and
practical applications and methods used in real navigation.
This subject won't die and be buried by anyone.
Mr. Reed,I read your post with great interest this morning concerning star
to star sights.The proceedure you talk about useing I've read in a few of
the older navigation books but never really gave it more thought.Maybe I'll
try it in the future for something to do.When is part 2 going to be posted?

   

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