# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**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"