NavList:

I don't have time at the moment to "work" these sights, but I will comment on Deneb.  Just by looking at it, is in the unfortunate place of being too high to use the ex-meridian method as the formula will fail us, and too far from the Zenith to plot circles of equal altitude on a reasonable scale.  For this star I will certain use standard reductions except for the "transit time" sight where a upper transit reduction can be made.

 

The lower transit example of Rigel Kent can be done with ex-meridians at lower transit if so desired, but frankly the method is fairly cumbersome to use for so many sights, so I will again use standard reductions until I find the one closest to lower transit.

 

Once I get some time (perhaps next weekend as I am working cargo all week) I will plug these numbers into my computer and see what I can get.

 

Jeremy

 

Sep 20, 2009


Dear Jeremy, and Dear All in Navlist,



You will find here-after the two Star LAN's I was able to shoot.

I know of 2 ways of solving them :

Either the so-called Marcq-Saint Hilaire Method,

or direct solution with specific algorithms such as the one used by Andrès Ruiz : see Navlist 9791 dated Sep 18, 2009

I trust that both are "extreme cases", but since I was (and still am) a Celnav ENTHUSIAST (like you in particular Jeremy !!!) I never wanted to miss an opportunity to shoot some exotic shots.

*******

DENEB

This first one occurred on Nov 16, 1979 on one of the then 2 French Navy Aircraft Carriers ( CLEMENCEAU or FOCH ? ) one evening when I was not flying my trusty F8E(FN) CRUSADER. It was almost by accident, as I noticed a few minutes earlier that Deneb would be full north of our vessel and I attempted to shoot it during the few minutes available.

Date 16 Nov 1979
Course 040° , Speed 22.0 Kts , Sea Current towards true direction of 050° at speed 0.5 kt
Height of Eye 28 meters, Pressure and Temperature supposed to be standard
DENEB is at the NORTH of the Vessel at its Upper Culmination
The following data were then published in the French "Ephemerides Nautiques"
BODY : DENEB
Verse Ascension : 049°49.0'
Declination    : N49°49'0
Greenwhich Hour Angle of Aries at 16h00m00.0s was 295°07.9'

All Heights already corrected for Instrument and Index Error. All times in UT

#1 - 16h26m06.0s   86°50'8
#2 - 16h28m02.0s   86°58'0
#3 - 16h30m12.0s   87°03'3
#4 - 16h32m31.0s   87°05'7
#5 - 16h35m18.0s   87°04'0
#6 - 16h38m43.0s   86°55'1
blank line on purpose here
#7 - 16h17m02.0s   85°54'3


Give DENEB Transit time, i.e. DENEB being true North of moving vessel and vessel's position at time UT 16h30m00.0s . Any indication on FIX confidence is welcome.

*******

RIGIL KENT

This one is my favorite ... and I had the opportunity to prepare it well in ahead of time with the adequate instrument.

Date 29 June 1981
Course 065° , Speed 18.0 Kts , Sea Current towards true direction of 095° at speed 2.5 kts
Height of Eye 25 Feet, Pressure 1026.5 Mb and Temperature +4°C (I remember that Warm clothes were much appreciated)
RIGIL KENT was at the SOUTH of the Vessel at its LOWER Culmination
The following data were then published in the French "Ephemerides Nautiques"
BODY : RIGIL KENT
Verse Ascension : 140°24.8'
Declination    : S60°45'7
Greenwhich Hour Angle of Aries at 08h00m00.0s was 037°19'0

All Heights already corrected for Instrument and Index Error. All times in UT

# 1 - 08h15m00s0     20°05.5'
# 2 - 08h30m00.0s   19°43.9'
# 3 - 08h42m00.0s   19°30.4'
# 4 - 08h55m01.0s   19°19.7'
# 5 - 08h59m34.0s   19°16.9'
# 6 - 09h03m12.0s   19°15.0'
# 7 - 09h12m42.0s   19°11.6'
# 8 - 09h17m53.0s   19°10.6'
# 9 - 09h23m47.0s   19°10.3'
#10 - 09h26m24.0s  19°10.4'
#11 - 09h30m00.0s   19°10.9'
#12 - 09h45m00.0s   19°16'1
#13 - 10h00m00.0s   19°26'7
#14 - 10h15m00.0s   19°42'7
#15 - 10h30m00.0s   20°04'0

Give RIGIL KENT Transit time, i.e. RIGIL KENT being true South of moving vessel and vessel's position at time UT 09h30m00.0s  . Any indication on FIX confidence is welcome.

*******
I will publish both results shortly.

*******

LAST NOTE : I have read quite a few things about "LAN's" on NavList with "pro's" and "con's" equally ( and sometimes "fiercely" :-)) convinced that LAN's are very good or are just "junk" .... Well, the truth lies somewhere in between, just because when you have nothing but an opportunity to shoot a LAN, it is certainly better than nothing at all. Therefore, if some readers are interested, I can offer my  comments on own experience (I shot about 85 LAN's in 7 years at sea, some of them (2.5 years) were as Ship conning Officer and the greatest part was when I was a Fighter/Attack Pilot and not flying on these days, evenings or nites)



Enjoy !!!


Antoine


Antoine M. "Kermit" Couette

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