Yachtmaster ocean requirements

[BruceDanforth]

I did have selected stars but I was in the southern hemisphere and it didn't help much to be honest. Next time I am going to spend sometime working out how to find things better before I get there.

Per Ardua Ad Astra :encouragement:

 

[Uricanejack]

Don't forget this bit...



For me, that involved constructing a Pelorus, for the relevant boat's bulkhead compass did not have a shadow pin, and doing the simple calculation of the Sun's Amplitude ( true bearing at astronomical sunset/sunrise ) for my twice-daily compass check.

My examiner was well pleased with my lash-up/recycled Pelorus, checked simply that I understood it, then pulled his own out of a cupboard and spent the rest of our time comparing 'boys toys'.....

That is a pretty impressive pelourus.
I recently found a gold special hand bearing compass from Saura marine Instruments of Tokyo with a prism.

 

[Uricanejack]

Selected Stars does it for you. Armed with a rough EP at the observation time, you can figure LHA Aries plus a couple either side, then look up whats on view.

Ive often drawn a rough sketch with big figures on a whiteboard. Ships head, relative azimuth of the stars plus their approx. altitudes. Takes practice to get more than 2, but can often be cut by a nice fat planet, or the Moon.

Theyre in much the same place for days on a long trip, its just mustering the enthusiasm to do it when your scrathcher calls.....

+1 tis the way to go. Use the tables for selected stars and draw a diagram of where they are then preset the sextant to the approximate altitude. don't try and get all 6
just go for the best 3 and take your time

 

[laika]

From the requirements:

Navigational records, completed on board a yacht on passages, out of sight of land showing that the candidate has navigated the yacht without the use of electronic navigational aids.

I used to take my sextant when I was playing mate on deliveries but assumed that despite the passages being trans-atlantic/trans-med I wasn't *actually* "navigating the yacht" without the use of electronic aids. I was taking sights not used for navigation whilst the skipper was setting the course according to nothing *but* electronic aids.

Given that I doubt that sailing school instructors doing "yacht master ocean qualifying passages" on a schedule never peek at the GPS but instead navigate according to a student's sights, would I be correct in thinking that there's a liberal interpretation of this requirement?

also...+1 on jdc's statement about shooting stars being rather easier after a few evenings of watches getting into the swing of where everything appears

 

[oldbilbo]

That is a pretty impressive pelourus.

Yup! I found the device - a 'dumb compass' - in a scrapyard I used to frequent, which would take in wagon-loads of remaindered naval stores from the RN warehouse-tunnels under Corsham... all legitimate, as the scrapper company would have bid/paid a nominal sum and frequently got startling value for their bids.

Anyhow, this was part of a wing-bridge setup from some Cold War destroyer, and I recognised it for what it was. It was easy to affix a means of clamping the thing to the boat's coachroof, align the lubber line, then take Relative Bearings of e.g the setting sun. The difficult bit was reading the main steering compass with any accuracy such that the resultant calculation of Ship's Heading was reasonably reliable. But then, all Nav Instruments work was about reducing the inevitable errors as much as possible.

Comes into its own when doing a proper compass swing in a quiet anchorage.

 

[BruceDanforth]

Next time I try a starsight I will get a better sextant. My one doesn't have any lenses in the 'telescope' bit as it is a Davis 'lifeboat' sextant so it just has a tube. It was easy to rack the sun down to the horizon but stars seemed to get fainter and fainter the more I pulled them down and it made things rather tricky.

 

[alant]

And with the wonders of tablets, despite enjoying a cheeky lunchtime pint I have pub249 voL1 to hand, looking at Navigational Stars, Right hand side "ordered by SHA" - is that what you use?
I've sort of got my head round it, but do need to do a load more work in this area.
Ta

There's also a planning pro-forma you can use.

 

[alant]

I tried to be a smart-alec and include a moon-sight for my OYM. Hopeless! Since then I've tried several times, but never got good results.

I've also found stars quite tricky, even when a suitable one has been identified spotting it through the sextant is not that easy. Respect to those who do this.

But I've managed Venus and Jupiter, which are easy to identify. They are bright enough that on a calm night they will sometimes illuminate the horizon well enough for a sight even after twilight.

I asked Tom Cunliffe about these & even he finds them difficult/unreliable.

 

[GHA]

Just spotted a possible hiccup...
__
The candidate must provide the examiner with:
Navigational records, completed on board a yacht on passages, out of sight of land showing that the candidate has navigated the yacht without the use of electronic navigational aids.
--
That's not going to be easy, this is a delivery and highly likely the boat will have ais and an electric autopilot so no way will the GPS get turned off.
Will the examiner really expect for the GPS to be off for the passage or would evidence oof the calcs and you know what you're doing be enough?

Ta

 

[Skylark]

From the requirements:


I used to take my sextant when I was playing mate on deliveries but assumed that despite the passages being trans-atlantic/trans-med I wasn't *actually* "navigating the yacht" without the use of electronic aids. I was taking sights not used for navigation whilst the skipper was setting the course according to nothing *but* electronic aids.

Given that I doubt that sailing school instructors doing "yacht master ocean qualifying passages" on a schedule never peek at the GPS but instead navigate according to a student's sights, would I be correct in thinking that there's a liberal interpretation of this requirement?

also...+1 on jdc's statement about shooting stars being rather easier after a few evenings of watches getting into the swing of where everything appears

I did my qualifying passage as mate. The boat was navigated by GPS but I kept a separate, a parallel log using traditional methods. I didn't use commercially available Plotting Sheets as I drew my own on A3 paper. My starting point was a position taken from the chart of our last fix from land, then used DR from ships log (compass and log) adjusted by sun-run-(Meridian passage)-sun each day.

I presented a completed navigation log to the YMO Examiner. I didn't use a proforma for sun sights as my logic seemed to work slightly differently to most of those readily available. I'm not sure if everyone does the same but, for example, when taking a for noon or after noon sun sight, I typically would try to take 5 or 6 sights over, say, 20 minutes. I'd then plot the altitude versus time curve and pretty much pick any that sat nicely on the line, maybe my lack of confidence in my ability to take a decent sight right out of the box.

I'd already done the YMO Shorebased course so I didn't have to do the theory test.

Discussing the navigation log was only a small part of the oral exam. For example, we talked about the wisdom (maybe lack of) of one of the crew wanting the proverbial 10 pints and a curry the night before cast off. We talked about how to replace a nav light bulb without a pesky screw falling overboard. We talked about bringing down the sails for a condition inspection. As you'd expect, we talked about provisioning the boat, route planning, meteorology and TRS, quadrants and so on.

To be honest, it was not a stressful experience at all. We had an hour or so chat over a mug of tea and my examiner offered a lot of useful, new information.

 

[GHA]

Cheers! Missed laika's post, ta.

 

[Neil]

Next time I try a starsight I will get a better sextant. My one doesn't have any lenses in the 'telescope' bit as it is a Davis 'lifeboat' sextant so it just has a tube. It was easy to rack the sun down to the horizon but stars seemed to get fainter and fainter the more I pulled them down and it made things rather tricky.

Try practicing star sights at home with a dish of oil as an artificial horizon! - possible with only the brightest stars, the reflection is so dim. It helps if it's one of the first ones out - less chance of losing it in a well populated star field.

 

[oldbilbo]

I typically would try to take 5 or 6 sights over, say, 20 minutes. I'd then plot the altitude versus time curve and pretty much pick any that sat nicely on the line, maybe my lack of confidence in my ability to take a decent sight right out of the box.

That's a traditional and time-honoured approach which, the experts say, produces a more accurate result than "Just the one, Mrs Wembley!".

You might take this a step further and AVERAGE the several Hs readings and their times, discarding the odd one - or two - that are well off the curve and clearly 'wildcats'. This is an ever more accurate technique, and the 'spread' along the curve gives you an indication of the quality of your sights.

Another useful technique for 'morning stars' is the selection and use, from Selected Stars, of just TWO fat stars with azimuths close to 90° apart, and in parts of the sky where a dark horizon is still available. Some like to have two PAIRS ready for use, in case cloud obscures the first choice....

Call these two stars A and B, then shoot them A : B: A: B: A ( 5-shot sandwich ) or, if time and light conditions permit, A : B: A: B: A: B : A ( 7-shot sandwich ). Average the A's, then average the B's, resolve and plot.

An enhancement is the choosing of a star-pair where the azimuth of one lies along your track, while the azimuth of the other lies 90° to your track.

 

[AndrewB]

Another useful technique for 'morning stars' is the selection and use, from Selected Stars, of just TWO fat stars with azimuths close to 90° apart, and in parts of the sky where a dark horizon is still available. Some like to have two PAIRS ready for use, in case cloud obscures the first choice....

Call these two stars A and B, then shoot them A : B: A: B: A ( 5-shot sandwich ) or, if time and light conditions permit, A : B: A: B: A: B : A ( 7-shot sandwich ). Average the A's, then average the B's, resolve and plot.

Sorry if I'm being slow on the uptake, but what's the reasoning behind this approach? (I always thought 3 stars were desirable for a good fix).

 

[jdc]

...I always thought 3 stars were desirable for a good fix....

The vast majority of astro navigation is done with only one star: the sun. Certainly for the YM Ocean requirements there's no need at all to do multi-star sights simultaneously.

Astro nav is essentially a process of running fixes: one gets a position line (PL) from a sight (at right-angles to the heavenly body's azimuth). Then one either finds a different body or the same one at some time later whereby the PL is now at a convenient angle to cross the first one. One has to displace the previous PL by the distance moved between sights (hence being able to work out departure is also a requirement btw). Errors are not cumulative.

I usually cross an evening star sight with that from the last sun sight, or a morning star sight with last night's star sight.

(in case interesting here's a link http://www.awelina.co.uk/sextant/reduction_tables/ReadMe.pdf to some pre-computed tables and how I think about the 'problem')

 

[oldbilbo]

Sorry if I'm being slow on the uptake, but what's the reasoning behind this approach? (I always thought 3 stars were desirable for a good fix).

All 'old-fashioned' and pro-trained navigators had to learn - in some depth - the 'Uses, Limitations and Errors of a Single Position Line'. Among all that was reasoned statistical argument that one's actual position would only very rarely be ON the single line of position ( LOP ). However, where it was possible to measure several simultaneous LOPs from the same source and average them, the 'bands of error' calculated by statistics would be very much reduced in width ( i.e. more accurate ), so that one's confidence in the use of that LOP in determining probable position ( and thus displacement from hazards ) would be enhanced.

A Two-Position Line fix would be better than a Single LOP, and not as good as a Three-LOP fix.

It is readily shown, from a study of 'Bands of Error', that it is perfectly possible for the actual position of the observer to lie outside the triangular 'cocked hat' produced by a 3-LOP fix.... and this was validated many, many times by simultaneous precision radar fixing.

However, where it was possible to take several LOPs from two sources simultaneously, then statistically ( and in practice ) the resultant Two-LOP Sandwich fix would be more accurate/reliable than a straight 3-LOP fix.

This could be done, on a ship/proper yacht by having two observers using two sextants at the exact same time, or by one observer adjusting one shot to the time of the other..... or by bracketing A/B/A/B/A as indicated above, with the fix time taken as that of the middle shot.

That was how the Vulcan was navigated at high level, much of the time, and it was a very effective process, shown by the number of times we/the RAF won NATO Bombing Competitions against the best the yanks could field.

This can be explored, should anyone so wish, by a detailed study of 'Bowditch' or 'AP3456G - Theory and Practice of Air Navigation'.... all the while remembering that ALL fixes derived from satellites are a 'mash-up' of multiple LOPs, a 'consideration' of potential errors and inaccuracies, and a rejection of those LOPs that are deemed sub-optimal. Exactly what a pro navigator would be doing 50 years ago....

Just as 50 years ago, when a pro nav would look at a 3-LOP or 2-Star Sandwich fix and say, "That's where we are - maybe", and make an allowance for that 'maybe', today a pro nav will look at a satellite-derived fix and still say "Maybe". While the numbers in the stats arguments have changed, the underlying principles have not.

 

[jdc]

I wholeheartedly agree OldBilbo, and if requiring an accurate position, for instance because closing an unlit shore during the night, multiple sights, possibly enhanced by your method, would be invaluable. But in the context of YM Ocean requirements too advanced or esoteric I think. I estimate the simple sun-run-whatever's handy method to give an error of 1 sigma = 1.5 miles at all times unless it's very rough.

Add more complicated things by all means - I've used multiple stars and planets and even tried lunar distances, but I have to admit it was only ever for the love of it. So I like to have a simple base methodology - one I have used for real on small boats on short-handed ocean passage when we had no electronic position fixing - which with the minimum of effort, opportunity for error and engendering of seasickness will get one to a landfall well enough.

On a similar vein, I eschew encumbering newcomers to the art with the complication of noon sights (why learn two methods, is your wrist watch broken? And if it is, what's the strategy for getting home then? Running down the latitude? No point teaching or examining one small thing unless in context).

However you (at least I think you raised it) are dead right that the examiners demand evidence of a compass check by azimuth. A complete anachronism imho; has anyone in a modern plastic yacht ever had a new deviation appear on passage which this technique spotted? If it is deemed important, it would be much better to devote a section of the exam and/or syllabus to swinging a compass and constructing a proper deviation card, using the azimuth of the sun being only one method among several (and if you set out on a passage without a deviation card then you should fail the assessment anyway!)

 

[AndrewB]

This could be done, on a ship/proper yacht by having two observers using two sextants at the exact same time, or by one observer adjusting one shot to the time of the other..... or by bracketing A/B/A/B/A as indicated above, with the fix time taken as that of the middle shot.

OK, with you now Oldbilbo.

Though achieving the same average for a set of bracketed observations on two stars is well beyond my humble skills. Shooting a star for me, is more a case of : "Nearly there ... damn, overshot ... now, now, NOW, ... no bother I'm on the wrong star ... hang on a mo ... you've stuck your elbow in the way ... OK, now ... GOT IT ... did you get the time ... ****! I'd better try again." Average 7 of those!

 

[oldbilbo]

I largely agree with 'jdc'.... except, someone going for YM Ocean should not be considered a beginner. Just consider what the term/label implies....

The members of the Yachtmaster Standards Panel have aeons of experience, each and collectively. It is their task to determine what is fit and what isn't, and neither they - nor I - consider that, at that level, there should be 'watering-down' of the required depth of experience, the knowledge, and the quality of judgement of candidates. The RYA's training people seem to think otherwise, for they sell courses, and their supporters - the sea school proprietors - run them. There lies the conflict of responsibilities.

I recall that, many years ago, the first Principal of the SCPR's Mountain Centre, Eric Langmuir, was asked what the standard should be for the award of the new Scottish Mountain Leadership Certificate. He replied "The question I will ask is 'Would I let that person take my children onto the Scottish hills?'"

I hold that that is a perceptive guideline relevant to the question of Yachtmaster standards - inshore, offshore and ocean.

As for the merits of different navigation techniques, provided one starts with a sound foundation AND is made aware that there is more, much more, if the candidate seeks to know, understand and do more, then that should suffice. As a start.

The esoterica of which form of astro fix is better than another, how best to hone one's Deduced Reckoning into a skill which can be relied on to get one home when all else fails ( yes it does, now and then. ), or whether the ability to turn on a colour plotter is any substitute for being able to construct a reliable fix from a range of sources, determine a prudent Most Probable Position, then shape a course which keeps one's guests and their souls together as nature intended.... all remains a fruitful topic for discussion, even divergence, among experienced practitioners. As it should be.

However, we should beware of 'the tail wagging the dog'.

 

[GHA]

Anyone care to share their proforma shight reduction sheets?

So I can steal


I mean plagiarise....