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Old 25-01-2013, 10:24   #46
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You mean like a blind man with paper charts... and not in Braille
Lol you've got it! the list reminded me of the sort of joke that involves a list. The if vegetable oil comes from vegetables, and olive oil from olives, where does baby powder come from type.
I'd like to see such a list for boats now, with funny names for what things are when a needed component is missing.
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Old 25-01-2013, 10:30   #47
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pirate Re: Sextant Newbie?

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On land I'd have both a lighter, and fire steel, only needed the latter once was good to have then.
Nothing worse than baccy n papers and no fire...
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Old 25-01-2013, 10:35   #48
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Re: Sextant Newbie?

I love the way everyone pro-sextant conveniently forgets that you CAN break a sextant. And when that happens, you're left with the same navigation tools that you have when your GPS breaks.

Hopefully you packed a sunstone as a backup for that occassion.
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Old 25-01-2013, 10:35   #49
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Re: Sextant Newbie?

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Nothing worse than baccy n papers and no fire...
Maybe a beach, a bonfire, a bottle of wine and no corkscrew?
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Old 25-01-2013, 10:42   #50
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pirate Re: Sextant Newbie?

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Originally Posted by hellosailor View Post
I love the way everyone pro-sextant conveniently forgets that you CAN break a sextant. And when that happens, you're left with the same navigation tools that you have when your GPS breaks.

Hopefully you packed a sunstone as a backup for that occassion.
Thats when the needle, cork and bowl of water come into play...
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Old 25-01-2013, 11:16   #51
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Re: SExtant Newbie?

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There's a huge amount of wise information in this long post by GrowleyMonster; however, some may not agree with the inherent inaccuracy of plastic. I can not speak with my own knowledge of the effects of the temperature expansion coefficients of the plastic and metal or to the results of these characteristics, but my own use of a plastic Davis sextant placed me regularly within ten miles of my actual position. Some may not consider this as a good record of accuracy, but I think it's a realistic expectation for sextant position fixes.

I think most of us use what we have. I certainly enjoy the accuracy of GPS, but I keep a thought to my running dead reckoning and I write down my known times and positions.
A plastic sextant, as I noted, could possibly, in a stretch, be regarded as a satisfactory backup navigation tool if you simply can't afford a metal one. But I still insist that greater accuracy in the instrument is to be preferred for learning purposes. Yes, a 10 mile long triangle or even a perfect pinwheel that is nevertheless 10 miles off, can be accurate enough for mid ocean navigation. However, there are a host of navigator's errors that could give you the same 10 miles off, and you will not spot those errors when you can just blame them on the instrument and be satisfied with them. If you don't spot your beginner's errors, you won't know to correct them. When a careful round of sights in good conditions gives a fix that is found to be off by that much, you know to look at your math or the time or your selection of data from the tables or possibly your care in taking the sights, if you know that your instrument could not possibly be that much off. FWIW I once met a retired RN guy who sailed from England to Belize with a plastic sextant, a wristwatch, plotting tools, sight reduction tables and the almanac, approach charts, and hand drawn plot sheets for mid-ocean, and nothing else in way of navigation equipment. Zero electronics other than a VHF. I don't doubt that a plastic sextant can be used for navigation because I know it has been done. I do very much doubt their suitability for the self taught navigator to learn with, if he is to develop a high degree of skill.
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Old 25-01-2013, 11:37   #52
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Re: Sextant Newbie?

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Originally Posted by hellosailor View Post
I love the way everyone pro-sextant conveniently forgets that you CAN break a sextant. And when that happens, you're left with the same navigation tools that you have when your GPS breaks.

Hopefully you packed a sunstone as a backup for that occassion.
Redundancy doesn't mean that the backup won't fail, but it's probably wise not to have a backup that has exactly the same vulnerability as the primary. As others have pointed out, if for whatever reason the GPS fails to acquire satellites, it's likely that the backup GPS will have the same problem.

But the probability that first the GPS will fail and then you will drop and break the sextant seems a far more remote possibility.
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Old 25-01-2013, 11:55   #53
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Re: Sextant Newbie?

Several years ago I was heading north on the west side of Vancouver Island and my GPS went out on me in a storm, and of course I did not happen to have a hand held GPS as a back up. I did have a sextant (well two actually), but I didn't see the sun for a couple of days. Still I had my dead reckoning skills, a decent compass, and a reasonably good idea of where I was when the GPS failed--and calmly reminded myself that Lindbergh flew the Atlantic using DR and arrived fairly close to where he wanted to be . I eventually got a noon sight a few days later and shortly thereafter traced the GPS problem to a bad connection and corrected that.
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Old 25-01-2013, 12:02   #54
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Re: SExtant Newbie?

I can tell that your bait is not going to be tastey.
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C'mon. Some things are easy for some and more difficult for others.


b.
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Old 25-01-2013, 15:27   #55
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Re: Sextant Newbie?

Johnny--
Boy, lots of advice here from all sorts, and most not too much on where to learn. My wife and I sailed from England to California back in 1977-78, and before we left, we taught ourselves celestial navigation with the best book in the world: Ocean Navigator, by Kenneth Wilkes:

Ocean Navigator: Kenneth Wilkes: 9780713639247: Amazon.com: Books

This is top notch, completely self contained, easy to read, easy to learn. He tells you everything you need to have such as the sextant and the sight reduction tables, but there are excerpts in the book so you don't need to buy everything right away. It's an excellent book.

On our voyage, we bought the new top of the line Davis plastic sextant (at the time) and that suited us fine. Plastic sextants are easy to handle because they are so lightweight. We did running sun sights the whole way across the Atlantic and the Caribbean, and we easily got where we wanted to go. We learned every type of sight in the book, made crib sheets for the calculations, but running sun sights (one in the morning, one at noon) were sufficient to cross oceans.

Good luck, you'll have a great time.

Eric
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Old 25-01-2013, 15:57   #56
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Re: Sextant Newbie?

Now that you have had enough about which sextant or method is best. Along with how much GPS is enough or too little and the dire depths you must be in to use a sextant.

You must enjoy the William F. Buckley Jr. video. Whether you have or will ever have a sextant in your life you must watch his video. Politics aside, he was a sailor.

It is worth listening to him talk about "Celestial Navigation" even if you do not own a sextant. You will learn quite a lot though. It is available through Netflix.
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Old 26-01-2013, 02:12   #57
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Re: SExtant Newbie?

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Have you read Letcher's method of Lunars, much simpler than the traditional method, less dependent on good sextant technique those potentially very tedious and time consuming.
If you dont have the tables and get frustrated with doinglunars anyway, you can just use an assumed time and shoot the moon and two other bodies and reduce normally. Plot your LOPs and advance or retard for a fix. For greater accuracy shoot several times and average them. Make sure your height of eye is correct cause your dip is critical, and record from the top of the swells cause that iswhere your horizon is. Must be calm conditions. Your two other than moon LOPs will cross at close to the correct latitude. Oh, and use stars not planets. The moon LOP may pass considerably east or west of the crossing of the other two. Fiddle around with the time correction as you recalculate until you find a time correction that gives you a pinwheel. Apply that correction to your clock time for subsequent navigation operations if it is significant. The method is not pinpoint accurate so keep track of your corrections. If your watch normally losesor gains 10 seconds a month then a lunar correction of a couple minutes is obviously suspect.

Btw i have never yet had need of this method and chances are good nobody else here will, either. High geek factor,

Of course if you have some way of knowing your longitude, finding the time is elementary and there are several obvious methods.
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