Cheapest workable sextant

[RichardS]

Anyone used to working with a lathe or milling machine would do that without thinking.

..and tuning a guitar!

And setting the time on your watch ..... always go a few minutes just beyond the time you want and the wind back to it.

Richard

 

[roblpm]

I've always finished by turning the micrometer drum in the same direction before reading... didn't think to do otherwise

Interesting little article here showing how Plath and then Tamaya and Astra designed things mechanically to minimise backlash..

Sextantbook description of backlash

To the original poster.. Did you manage to find a cheap enough sextant?

I might have a spare ebbco plastic one on board that you could have for the cost of postage..

Martin. Pm sent. I am extremely undeserving though!

 

[Mark-1]

This was pretty cheap made from bits around my house:

Without any knowledge of Astro-nav beyond the kind of stuff a total layman would know I got within 12 miles of my Latitude at first attempt.

After reading up a bit to learn how to work it all out for real I was a few dozen miles off my correct lat/long.

 

[Iliade]

This was pretty cheap made from bits around my house:

Without any knowledge of Astro-nav beyond the kind of stuff a total layman would know I got within 12 miles of my Latitude at first attempt.

After reading up a bit to learn how to work it all out for real I was a few dozen miles off my correct lat/long.

If you put the plumb bob into a glass of water it might even work at sea ;-)

 

[john_morris_uk]

If you put the plumb bob into a glass of water it might even work at sea ;-)

And there again...

 

[phanakapan]

Backlash was not mentioned in my RYA ocean course. We didn't even get to handle a sextant, yet alone take a sight with one.
I still managed to achieve decent enough noon sights on my way back across the Atlantic, mostly by taking quite a few before and after sights, plotting a graph and getting a good average. (Using a Davis 25 given to me for free in Sint Maarten- and just for fun as we had 2 plotters and 3 other GPS s on board....!)
(Edit using cunliffe and blewit and vague memories of the course)

 

[john_morris_uk]

Backlash was not mentioned in my RYA ocean course. We didn't even get to handle a sextant, yet alone take a sight with one.
I still managed to achieve decent enough noon sights on my way back across the Atlantic, mostly by taking quite a few before and after sights, plotting a graph and getting a good average. (Using a Davis 25 given to me for free in Sint Maarten- and just for fun as we had 2 plotters and 3 other GPS s on board....!)
(Edit using cunliffe and blewit and vague memories of the course)

You must be referring to the RYA Ocean Theory course. I'm disapointed that wherever you took the course didn't allow the students to even handle a sextant. I'm an Ocean Instructor and Examiner and I will always take a sextant (and encourage students to bring theirs along if they have one) as correcting the instrument for errors and discussing the actual handling of it is much more interesting and hopefully instructive with the real thing in your hand.

You might be able to take the theory course without handling a sextant for real but that only exempts you from part of the RYA Ocean Exam proper. To get your RYA Yachtmaste Ocean ticket you need to do your qualifying passage and take some sights and find your position. The very minimum is a merpass of the sun, run on with a sun sight taken a few hours later or before and a compass check by azimuth of a heavenly body etc. Position finding, sights and sight reduction is only 1/3 of the exam. 1/3 is planning and preparation (world meteorology, ocean currents, routing, victuals etc etc) and 1/3 is management of the yacht at sea on an Ocean passage. The point I'm making is that you can't be a Yachtmaster Ocean without using a sextant in anger.

PS My £150 eBay metal sextant has no discernible backlash, but I agree with those who say one should automatically always rotate the adjustment screw the same way as one takes the reading as a matter of habit. (With me it's from using lathes/milling machines years ago.)

 

[phanakapan]

You must be referring to the RYA Ocean Theory course. I'm disapointed that wherever you took the course didn't allow the students to even handle a sextant. I'm an Ocean Instructor and Examiner and I will always take a sextant (and encourage students to bring theirs along if they have one) as correcting the instrument for errors and discussing the actual handling of it is much more interesting and hopefully instructive with the real thing in your hand.

You might be able to take the theory course without handling a sextant for real but that only exempts you from part of the RYA Ocean Exam proper. To get your RYA Yachtmaste Ocean ticket you need to do your qualifying passage and take some sights and find your position. The very minimum is a merpass of the sun, run on with a sun sight taken a few hours later or before and a compass check by azimuth of a heavenly body etc. Position finding, sights and sight reduction is only 1/3 of the exam. 1/3 is planning and preparation (world meteorology, ocean currents, routing, victuals etc etc) and 1/3 is management of the yacht at sea on an Ocean passage. The point I'm making is that you can't be a Yachtmaster Ocean without using a sextant in anger.

PS My £150 eBay metal sextant has no discernible backlash, but I agree with those who say one should automatically always rotate the adjustment screw the same way as one takes the reading as a matter of habit. (With me it's from using lathes/milling machines years ago.)

I don't think I claimed to 'be' a Yachtmaster Ocean? I did do the RYA Ocean theory course- and as you say, it included much more than just celestial navigation; in fact a very useful course, fairly cheaply obtained at a local authority night school- and generally very well taught, to a very mixed lot of students, some of whom didn't sail and were just doing it out of academic interest.
I certainly used some of the knowledge gained from it in my 3 year, 30000 mile world circumnavigation. Although generally we just sailed along the pink line produced on the plotter, we had all the appropriate paper charts, pilot books, etc, a Walker towed log, hand bearing compasses, and used them alongside the plotter as belt and braces.
I have my sun-run-sun sights, a couple of moons and one awful attempt at stars carefully tucked away somewhere, with copious notes on what I think went wrong and right, and why- just in case I ever get round to having the chat with an examiner- maybe you! However, I seem to remember that there is a time limit, so it might not happen.
I loved having a go at the celestial navigation, it certainly made that leg more interesting.

 

[Neil_Y]

Cost I got a s/h Freiberger for £200, It's outlasted 4 GPS's three of which failed in action. I think a cheap plastic will get you there safely though as you plan your approach accordingly knowing that you might be 15-20nm out in Long. Practice at sea definitely helps with accuracy.

 

[john_morris_uk]

I don't think I claimed to 'be' a Yachtmaster Ocean? I did do the RYA Ocean theory course- and as you say, it included much more than just celestial navigation; in fact a very useful course, fairly cheaply obtained at a local authority night school- and generally very well taught, to a very mixed lot of students, some of whom didn't sail and were just doing it out of academic interest.
I certainly used some of the knowledge gained from it in my 3 year, 30000 mile world circumnavigation. Although generally we just sailed along the pink line produced on the plotter, we had all the appropriate paper charts, pilot books, etc, a Walker towed log, hand bearing compasses, and used them alongside the plotter as belt and braces.
I have my sun-run-sun sights, a couple of moons and one awful attempt at stars carefully tucked away somewhere, with copious notes on what I think went wrong and right, and why- just in case I ever get round to having the chat with an examiner- maybe you! However, I seem to remember that there is a time limit, so it might not happen.
I loved having a go at the celestial navigation, it certainly made that leg more interesting.

Wasn't suggesting you claimed YM Ocean -just clarifying for all readers of the forum the distinction. No knicks twisted please...

I'm still sorry that the course (no matter how well taught) didn't allow students the opportunity to actually handle a sextant.

I agree with you that celestial makes a leg more interesting. I usually get the sextant out of its box from sheer boredom on an Ocean passage. Eat sleep cook watch keep, read a book, clean, check boat over repeat in various orders until bored when I fetch the sextant from its stowage.....

 

[LadyInBed]

I bought an Ebbco in the early 1990s and used it regularly on a small dive rib to measure distance off (quite successfully).

I did the same but in the 1980s - used it horizontal along with a compass to put myself over a wreck, and it worked!

 

[mm42]

I bought a Freiberger sextant a couple of years back as they're a lovely thing to own. I am hoping to do the YM Ocean later this year and it will get used then but in the meantime it's a beautiful piece of engineering.

 

[ffiill]

I picked up my mark 15 Davis for about £10 missing a telescope or a sight tube and needing a new silvered mirror
They do occasionally come up on e bay being sold by people who dont have a clue.
Before that I had a lovely MAC which along with simex was post war Tamaya in disguise.
That cost me about £50 on e bay without a box having belonged to someones father,a merchant navy officer.The arc was as I recall a bit dirty and again I think I sent off mirror to be resilvered

 

[capnsensible]

I picked up my mark 15 Davis for about £10 missing a telescope or a sight tube and needing a new silvered mirror
They do occasionally come up on e bay being sold by people who dont have a clue.
Before that I had a lovely MAC which along with simex was post war Tamaya in disguise.
That cost me about £50 on e bay without a box having belonged to someones father,a merchant navy officer.The arc was as I recall a bit dirty and again I think I sent off mirror to be resilvered

Man who pay peanuts gets monkey........