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On 29 May 2001, at 9:45, Noyce, Bill wrote:
> > 1)  At the log reading of 89.6Nmi, what is the DR position?
> > --  -------------------------------------------------------
> Mid-Latitude Sailing using L=13d 20'
> TC = 263.7  dLat = 9.8' S  dep = 89 nm W  DLon = 91.5' W
> DR position = 13d 15.8' N 63d 1.6' W
OK
> > 2)  At the DR position what is the celestial phenomena that is
> starting
> >     at this DR Zone Time(ZT)?
> > --
> -------------------------------------------------------------------
>
> 18:27:00 + 10.3 hrs = 04:45 ZT 30 May
> At this time and position, I find the sun's altitude is -13d 58'
> -- still 2 degrees short of the start of Nautical Twilight.
> But if we're actually 1.5 degrees east of here, that would
> explain most of the difference.
Ok--it's MNT
> > 3)  What is the FIX position?
> > --  -------------------------
>
> Using the above DR position,
>
> Body      Fomalhaut    Polaris       Deneb        Vega
> GHA       36d  3.0'   342d 53.1'    70d 20.8'   102d  8.4'
> Decl    S 29d 36.9'  N 89d 16.1'  N 45d 16.8'  N 38d 47.0'
> Hc        39d 50.8'    13d 23.4'    57d 23.5'    47d  5.2'
> Az        149.1d         0.7d       350.4d       313.9d
> Int        58.2' T      14.8' A      32.4 A       75.0' A
Hmmm...something very wrong with the Polaris Dec. CAN'T be that high.
Polaris gives your latitude with its LOP.
> Pretty long intercepts, and a poor cut.  I used Ageton's
> method, and for Polaris found why it's not recommended for
> LHA near 90 degrees with high declination -- you end up
> trying to find an angle whose sine is about 1.0, and since
> the function doesn't vary rapidly there, the angle isn't
> established with any precision.  So instead of using
>       sin K = sin decl / cos R
> I tried
>                               cos T * sin R   cos T * cos d
>       cos K = cot T * tan R = ------------- = -------------
>                               sin T * cos R       cos R
> Is this Sadler's modification to Ageton's method?
>
> Anyway, I tried again with an AP of 13d 0' N 61d 30' W
> and got intercepts of
>   Fomalhaut: 0.3' A
>   Deneb:     0.3' A
>   Mars:      4.6' A
>   Venus:     0.1' A
>   Vega:      0.1' A
> and except for Mars, it looks like we're there.  I wonder if
> I made an obvious mistake here:
>          Mars
> GHA    114d 23.9'
> decl  S 25d 47.5'
> K     S 38d 42.0'
> Hc      25d 33.1'
> Az      232.8d
??? FIX
> > 4)   What is the TC and Dist from our FIX to the Aruba Gap
> >      (13d 50.0'N  70d 00.0'W)
> > --  ------------------------------------------------------
>
> Mid-Latitude (using 13d 25')
> dLat = 50' N  Dlon = 510' W  log(dep) = 1.69897
> TC = 275.7d  Dist = 499 nm
Hmm, TC is off. Check the FIX.
> > 5)  What is the Compass Course(CC)/Course-to-Steer for Aruba Gap?
> > --  -------------------------------------------------------------
>
> TVMDC, West is Best, add 11d: 286.7d
OK
> > 7)  What is the anticipated Speed Made Good(SMG) to Aruba Gap?
> > --  ----------------------------------------------------------
> Current essentially right on our tail, 9.3+0.8 = 10.1 kts
OK
> > 6)  What is the time enroute to Aruba Gap?
> > --  --------------------------------------
OK
> 2 days + 1h 24m
Dan Hogan WA6PBY
dhhogan@XXX.XXX
Nav-L Web Page: http://www.wa6pby.com
Catalina 27 "GACHA"

   

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