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Subject: Re: Silicon Sea: Leg 71 (belatedly)
From: Dan Hogan (dhhogan@XXX.XXX)
Date: Tue May 29 2001 - 15:45:08 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@XXX.XXX
Nav-L Web Page: http://www.wa6pby.com
Catalina 27 "GACHA"
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