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  #1  
Old 08-15-2008
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Sextant Advice, Please!

I will be leaving on a two-week cruise through the San Juan and Gulf islands tonight.

Which is a good thing.

What makes it even better is that I will be receiving a "loaner" sextant via UPS today, thanks to my brother.

I think that I want to learn to use the sextant on the trip.

However, I have no tables, nor books, nor much of a clue as to how to use the thing.

Even better is the fact that it's my birthday in a couple of weeks!

So, I plan to head to Captain's Nautical Supplies in Seattle today to pick up some charts that I need, as well as my new birthday presents.

Captains Nautical Supplies, Marine Charts, Marine Navigation, Electronic Charts


I plan to use my GPS for accurate time, I know I need tables and books.

So, I am asking for your help.

Do you have any advice as to what books/tables I will need?

Am I crazy for trying to do this, or will I be able to pick this up without formal training during the cruise?

I'm pretty geeky, but have almost no celestial navigation knowledge.

I think the stars are coming into alignment for me on this one and am wondering if I'm way off track here.

Any advice is appreciated.
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Old 08-15-2008
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You would need the Nautical Almanac and HP 229 for the Latitudes you will be in. And Dutton's on how to use it.
Plus there are some wonderful PC programs that can do the Almanac for you, giving you your daily data for the Sun, Moon, Planets & Stars and do the math for your sight reduction.
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Old 08-15-2008
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Don't forget a star finder so you'll know which stars you're looking at (and, therefore, which ones to look up in the tables).
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Old 08-15-2008
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My advice is to focus on the noon sight for latitude (which requires no tables...just an almanac) and a related meridian transit sight for longitude which also requires no tables, just an almanac. And, since both of these types of sights use the sun, I'm sure you'll have no trouble identifying it :-)

Start with these. They're simple, and will give you a reasonable position fix around noon.

If you'll shoot me an email to bill at wdsg dot com I'll email you the simple forms needed to compute these two types of sights, along with an explanation.

Good luck, and good sailing.

Bill

BTW, the tables are a good idea for later on when you want to tackle more complex sight reduction. They're needed for the complex spherical trig solutions, but are not needed when you are using meridian transit methods.

Final note: GPS time isn't as accurate as you probably think, for reasons too convoluted to cite here. A good digital watch and/or a radio which can receive WWV signals is better (though GPS time probably is good enough for use with a sextant since the resultant position fix won't be all that accurate, anyway). Remember, a 4 second error equals one nautical mile.

Last edited by btrayfors; 08-15-2008 at 02:13 PM.
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Old 08-15-2008
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Thanks, All!

Bill, thanks for the information.
This is really cool. I will try this.

My brother, who lives in Detroit, learned celestial navigation in the 1980s, but became discouraged, because he couldn't really go anywhere and always got the same readings...

I will range over 1000 square miles over the next couple of weeks, so I expect that I will get lots of different readings.

I am learning this as an offering to the Celestial Navigation Gods, who allowed my father and stepmother their safe circumnavigation without any celestial navigation tools or knowledge (Only Satnav and Loran back then for him).

http://www.sailnet.com/forums/cruisi...-bragging.html


Thanks,

David
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Old 08-15-2008
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We're headed out this weekend to Coronet Bay with some guests. I have a book explaining celestial navigation, the H.O. tables for our lattitude for the air navigation method and some work forms around here somewhere. If you're interested, we could meet either Hope Island or Coronet Bay and you could use them. Hard part would be getting them back though.
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Old 08-15-2008
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Thanks.. I plan to arrive at Hope Island around 1PM tomorrow. We'll probably be anchored on the north side. My son will be the one constantly on the rope swing. We'll head out for Stuart Island early Sunday.

I'm going to buy and keep the books, but it would be good to meet you, and perhaps you could tell me if my sextant is any good.

It's a dark blue 1984 Catalina 30.

David
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I'm going to buy and keep the books, but it would be good to meet you, and perhaps you could tell me if my sextant is any good.
I'm qualified to tell you if it will sink or swim, that's about it. I learned on $25 plastic sextant and an artificial horizon, so I don't have any experience with a "good" sextant.
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Old 08-15-2008
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we had astro navigation in school; you need a sextant, a watch, an almanac, basic calculator, a pen and a rubber (my teacher would say + beans for your brains); there's a lot, a lot of mathematics and of course sextant technique;
our teacher trained us with the moon, the sun and more or less on Altair star.
u'r not crazy to try this couse it's a must but a lot of mates didn't get it at first but everyone who says it's impossible it's just a lack of will or he/ she needs a teacher

Last edited by Karletto; 08-16-2008 at 12:36 PM.
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OK.. off I go. I'm headed off to the marine store. Thanks again,

David
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