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    Re: Silicon Sea: Leg 71 (belatedly)
    From: Dan Hogan
    Date: 2001 May 29, 15:45 EDT

    On 29 May 2001, at 14:22, Noyce, Bill wrote:
    > > > 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.
    >
    > What Dec. would you use for Polaris on 30 May?
    >
    > > Polaris gives your latitude with its LOP.
    I take it back. My head is still elsewhere.
    >
    > AP Latitude  = 13d 15.8'
    > Intercept    =     14.8' A
    >               ---------
    > FIX Latitude = 13d  1.0'
    >
    > I did it the long way because I'm not using Polaris tables:
    >
    > > > 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
    >       [mostly under 0.5']
    > > > and except for Mars, it looks like we're there.
    > >
    > > ??? FIX
    >
    > Sorry, I should have spelled it out.  With those small intercepts,
    > I was willing to take FIX = AP (13d 0' N 61d 30' W).
    >
    > > > > 4)   What is the TC and Dist from our FIX to the Aruba Gap
    > > > TC = 275.7d  Dist = 499 nm
    > >
    > > Hmm, TC is off. Check the FIX.
    >
    > Looking at your revised answer sheet, you have 286.8d for both
    > #4 (TC) and #5 (CC).  I think that's the correct CC, and hence
    > can't be the correct TC.
    Right TC= 275.7d...AAaaarrrrrgggghhhh!
    > > > > 5)  What is the Compass Course(CC)/Course-to-Steer for Aruba Gap?
    > > > > --  -------------------------------------------------------------
    > > >
    > > > TVMDC, West is Best, add 11d: 286.7d
    > >
    > > OK
    Dan Hogan WA6PBY
    dhhogan{at}XXX.XXX
    Nav-L Web Page: http://www.wa6pby.com
    Catalina 27 "GACHA"
    

       
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