Chuck, The sextant is just a sophisticated piece of equipment to measure an angle with the precision of a minute, one sixtieth of a degree. A sextant alone will not get you anywhere without a chronometer. Any sailor visiting England should pay a visit to the Greenwich Royal Observatory where you will see the original Harrison chronometers that resolved the problem of longitude (still functioning). If you're using old methods, you also need ephemeris and sight reduction tables. It is easy today to find a free piece of software or even build one yourselves with an Excel spreadsheet. What you need is the ability to understand the time equation and some fairly simple formulas. A good site to start with is Celestaire (http://www.celestaire.com/) whom will provide you with everything you need. You can also find pieces of free software on the net. Since I,m french I can only recommend you a very nice French piece of software you can download for free (http://olravet.fr/navastro.php). Very neat, it allows you to also plot the course, because don't forget, one of the key thing to understand is, one reading will not get you a fix. You need at least two reading to plot a position. I have myself two sextants that I cherish ( one old fashioned half mirror and a newer full mirror. Once you learned all the mechanics, this is when you'll discovered that getting a good reading out at sea with a two meter swell is the real challenge. Learning of this is fun, don't get discouraged.
Antoine (C&C 30, Cousin) Le 2013-01-27 à 13:24, Chuck S a écrit : > My understanding is that the sextant measures the angle between the Moon or > Sun and the horizon. If you're careful reading the solar or lunor tables it > gives you the latitude where you are. Longitude is something else. I know > it requires a good timepiece, but how does one convert the time to longitude? > > > Chuck > Resolute > 1990 C&C 34R > Atlantic City, NJ > From: "Frederick G Street" <f...@postaudio.net> > To: cnc-list@cnc-list.com > Sent: Sunday, January 27, 2013 12:16:33 PM > Subject: Re: Stus-List Mounting chartplotter now Compass Deviation > > Pricey little bugger… > > I picked up a slightly used Astra 3B several years ago on eBay, from a guy in > Malaysia. Nice wooden box (which I replaced with a Pelican case), and the > thing was smack on for calibration. One thing I did do was to replace the > old incandescent arc illumination lamp with a red LED; it required some redo > of the battery compartment in the handle, but I shouldn't have to change > batteries in a long time. > > Of course, it's not much use on Lake Superior -- as big as the lake is, you > can often see the mountains (large hills, actually) on the North and South > shores. I had a chance to run it through its paces on a trip to the Pacific > Northwest, where we actually had a decent horizon to play with. But I'd need > to get familiar with either the paper fix calculation charts or newer > celestial nav software in order to get even remotely proficient again. > > Still, it's a cool gizmo to keep around, in case I ever do get out to > bluewater; and it only cost me about $300 plus shipping. > > Fred Street -- Minneapolis > S/V Oceanis (1979 C&C Landfall 38) -- on the hard in Bayfield, WI :^( > > On Jan 26, 2013, at 8:44 PM, Richard Davis <rdavis2...@me.com> wrote: > > Here is a nice metal sextant. > > http://www.landfallnavigation.com/-nhu01.html?cmp=pricegrabber&pg=-nhu01&utm_source=-nhu01&utm_medium=shopping%2Bengine&utm_campaign=pricegrabber > > > _______________________________________________ > This List is provided by the C&C Photo Album > http://www.cncphotoalbum.com > CnC-List@cnc-list.com > _______________________________________________ > This List is provided by the C&C Photo Album > http://www.cncphotoalbum.com > CnC-List@cnc-list.com
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