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Old 18-10-2009, 17:01   #1
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Lightbulb Sextant Education

Hi! I have looked all over CF for a recommendation concerning a school that teaches not only the basics of sextants,(noonsite, reduction tables and a few star sites) but also how to use them to find distances to local objects and generally make them as useful as possible. I figure if I am going to use a sextant, I might as well use it in any situation that I can. Any old barnacles out there willing to teach such forgotten lore?
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Old 18-10-2009, 21:55   #2
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In Utah? Maybe this will be difficult. I got my training at my club, on Lake Ontario, from a guy who had done navigation from the '60s to the '90s on Caribbean-bound yachts. I could have also tried Canadian Power Squadron.

You can do a great deal, however, from books and by using one of the many "shortcut" (just adding, subtracting and looking up in the Almanac, which you'll have to buy) and publications like H.O. 249.

If you're land-locked, acquire an "artificial horizon" to replicate the sea when you are staring at a mountainside.
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Old 19-10-2009, 01:54   #3
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You might want to do a search for celestial or sextant in the search engine after migh signature. There are several threads on the subject but none with any current classes or schools listed.
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Old 19-10-2009, 02:26   #4
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There are lots of excellent tutorials online, which should suffice for first start.. I highly enjoyed this e-book on the subject (free of course)
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Old 19-10-2009, 03:48   #5
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Sextant Navigation requires the following

Almanac
Rapid sight reduction tables (available download free from US Government site)
accurate time
visible horizon (or bubble level)
plotting sheet
forms to do the calculations.
practice

I can offer the forms and plotting sheet (just pm me your email)

Tom Cunliffe's books on ocean nav are pretty much self explanatory.
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Old 19-10-2009, 10:34   #6
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Thank you for all the replies. I should say that I am on the coast (Bellingham, WA) about one week every two months. It is there that I devote my time to my Grandson and my boat. I am familiar with what is required, I was just hoping for a good school (that I would be willing to travel to) for hands on instruction.
If there is anyone up that way that wishes a student- I could provide a boat and a free cruise
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Old 19-10-2009, 11:01   #7
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For some self-study, you can go to Celestial Navigation Data for Assumed Position and Time — Naval Oceanography Portal and enter a sample lat-long-time and it'll give back Hn and Zn for you to plug into table and see if you get the right position.
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Old 19-10-2009, 17:56   #8
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From books.

Not difficult.

If you go for it as a back-up then remember to carry the almanac (a paper copy) and a trusty and adjusted Casio ... seen boats with Plath sextants... and little else ;-)

b.
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Old 20-10-2009, 03:37   #9
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I think it is hard for most folks to self-learn CN. A course is better in many ways. It's easy once one knows how, but the learning curve can be a bit steep without guidance.

Check out the USPS Squadrons -- their CN course is good. Example Seattle Sail & Power - Affordable high-quality boating courses. CN in the USPS system usually is an advanced course taken after obtaining pre-requisite courses, however perhaps they allow students in depending on prior alternative training or experience.

Might also want to see what StarPath has to offer, if you want to travel to take a course Starpath School of Navigation Title Page though I do not know whether they offer a CN course that one could do in a short period of time. Perhaps they offer a combination of home study/travel.
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Old 20-10-2009, 15:19   #10
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It looks like Starpath offers an excellent home study/online course. Has anyone here taken it and what do they think?
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Old 21-10-2009, 22:06   #11
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Originally Posted by s/v Beth View Post
I figure if I am going to use a sextant, I might as well use it in any situation that I can.
A sextant is mostly useful at measuring angles, vertical or horizontal I am sure some people may find other use for it.
There is not much to it, Davis cover it’s utilisation in a booklet of few pages and few weeks of daily practice will quickly make anyone a skilled operator. What is harder is to find your way through tables written by expert who have long forgotten the difficulty they had when they where beginner.

Coastal navigation.
Distance Off and Bearing.
Accurate fixes can be obtained from vertical angles to a known height.

Distance Off in miles = (height off object “in ft” x .565)/ Vertical angle in minutes.
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Old 23-10-2009, 03:07   #12
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Sextant is a great way to get a three-bearing fix: hold horizontally, measure the angle between two charted objects, and then measure a second angle from one of those objects to another charted object, go below, set the two angles on a 3-arm protractor (Weems and Plath), and then move the protractor around on the chart until the angles fit the scenario. I sailed recently with a former hydrographer who did that for routinely in small boats while running sounding lines. We played with the concept one day with our sextants and consistently got more faster, more accurate fixes that way than by shooting three bearings with a hand-bearing compass. Requires a chart table to plot the fix.
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Old 23-10-2009, 04:40   #13
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Even cheaper way to make the fix is to draw a line between the objects on the chart, do the geometry, find the centre of the circles, and draw in the two position circles with a drawing compass
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Old 23-10-2009, 06:25   #14
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Originally Posted by idpnd View Post
There are lots of excellent tutorials online, which should suffice for first start.. I highly enjoyed this e-book on the subject (free of course)
I've been reading this after you posted the link. It's clear and concise. Although I basically understand the theory, I have put off practice with the sextant because I am not close to a natural sea horizon. The e-book, however, has inspired me to set up an artificial horizon and play around with it this winter.
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Old 23-10-2009, 06:31   #15
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One important thing to do when using the sextant to measure the angle of a celestial body, is to slightly roll/rock the sextant in your hand as you have the body on the horizon. You'll ses the body describes an arc over the horizon, and you want it at the lowest part of the arc
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