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Old 23 November 2023, 14:36   #1
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Yachtmaster Ocean

Anyone here done their yachtmaster ocean theory (learning astro navigation)? I am doing a question and got a bit stuck.

I have an EP of 5005'N, 2010W and then a 2nd position that is on a bearing of 097T, distance 14.5M.

I've drawn a plotting chart for observations of the sun at 50 latitude and need to get the assumed positions correct for the observations - so have tried to plot the initial one and then done a course and bearing based on the plot to get the assumed position for the 2nd one.

I come up with 5003.5N, 1948W based on my drawing, but apparently the correct answer is 1942,6W.

I've even drawn the grid up in CAD to make sure my measuring isn't way off.

What have I got wrong? Thank you.
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Old 23 November 2023, 17:51   #2
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Ah! Worked it out. Thanks.
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Old 24 November 2023, 12:44   #3
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Ah! Worked it out. Thanks.
I did have a look at it & it was way over my pay grade tbh. Where did you get the numbers for the trig calc? I.e. the 89.8/75. Are these actual scale measurements off the drawing, or read off the X-Y axis?
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Old 25 November 2023, 12:32   #4
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Now I know the answer - I didn't have all the info in my question here.
Basically - I had 2 sights of the sun with an estimated position at the time the first one was taken.

For the 2nd sight, because you use an "assumed position" anyway, I hadn't updated my estimated position, assuming I could use my first EP anyway (it's a "thing" in astro navigation that you basically never use your exact position - you use an assumed position and then work out your delta from it).

So what I needed to do was take the closest point on the position line to the first EP, then do a course and bearing from that to give me a 2nd EP - and finally from that EP, compute an AP against which to then do calculated vs true altitude to get a position line for the 2nd.

And then we transfer the first position line based on our course and bearing (normal YM stuff) to give us a an intersection of the 2 sights and, hopefully, a fairly accurate position at the time of the 2nd sight.

It is interesting, but primarily, THANK GOD FOR GNSS. Navigating in a pre GPS, RDF and other electronic aids era was (sometimes literally, given that my uncle was posted on minelaying submarine in WW2) a minefield!
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Old 28 November 2023, 19:50   #5
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My lad has it and says the Celestial one is a bit hard to understand but he did his in USA
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Old 28 November 2023, 21:56   #6
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Yeah, I think I’ve got it now. It’s basically all gcse trigonometry, but a bit convoluted and not always easy to see the wood for the trees. Hopefully will pass in the next few days, just a couple more modules to learn
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Old 29 November 2023, 15:52   #7
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Yeah, I think Ive got it now. Its basically all gcse trigonometry, but a bit convoluted and not always easy to see the wood for the trees. Hopefully will pass in the next few days, just a couple more modules to learn
What tickets are you aiming for
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Old 29 November 2023, 16:00   #8
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Pretty much everything I can get - I've had a little spare time recently so have done Dayskipper theory, YM Coastal & Offshore Theory already. Still have to sit in front of the desk at the moment, so decided to do Ocean too. And will be looking for a place I can do my practicals in the new year.

Sailing, not power, but will probably do one of the week long courses - it's been a few years since I've done yachting so a bit of practice will be useful - although hopefully it'll all come flooding back. And I just quite fancy the craic.

Already have PB2, VHF - think I'll need to do a safety one to get the YM quali too.

Are there any other interesting and useful courses anyone would recommend?
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Old 29 November 2023, 16:24   #9
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Pretty much everything I can get - I've had a little spare time recently so have done Dayskipper theory, YM Coastal & Offshore Theory already. Still have to sit in front of the desk at the moment, so decided to do Ocean too. And will be looking for a place I can do my practicals in the new year.

Sailing, not power, but will probably do one of the week long courses - it's been a few years since I've done yachting so a bit of practice will be useful - although hopefully it'll all come flooding back. And I just quite fancy the craic.

Already have PB2, VHF - think I'll need to do a safety one to get the YM quali too.

Are there any other interesting and useful courses anyone would recommend?
A friend of ours did her Yachtmaster as a liveabourd cruise around the UK. It cost around 2k iirc & involved a 3 week cruise around the UK, she did both her theory & practical side by side. Was pretty intense by all accounts, but she enjoyed it & passed.
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Old 29 November 2023, 16:34   #10
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Yeah, don't quite want to go to that extent to re-do all the theory - but certainly yes to a liveaboard deal for, I think 8 days, would be great. And not in the solent! Either scotland or the SW, so I get to see some new places too. But depends who is offering what - I'll look to do it fairly in the new year if I can.

I've hated sailing for the last 20 years - did a lot of dinghy racing in my teens, but ultimately overdid it and became "all about the race". And too much time on my father's macwester kinda put me off cruisers - imagine it taking a full day to get from Portsmouth to Poole, if not 2 if you get the tides wrong and stop overnight in Yarmouth.

But ultimately, I like a challenge and am doing all this to, hopefully, set myself up to eventually do a transatlantic crossing, if not more. We'll see.
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Old 29 November 2023, 20:51   #11
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Sounds like a great plan, well done. I did my day skipper about 4 years ago, theory online and then a practical with BOSS sailing, brilliant experience with two completely different tutors, one raced yachts in his younger years, the other was an X tornado pilot. Sailing, for me, is for hot weather countries. Nothing quite like chartering in Greece.
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Old 29 November 2023, 20:55   #12
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Yes, good point. Part of the goal of the quali’s is also to allow me to charter stuff with with family abroad too.
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Old 29 November 2023, 21:57   #13
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From what my lad has done its all pretty intense and expensive but he did motor yacht stuff up to 3,000 tons
Think up to press circa 18k cost wise
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Old 30 November 2023, 08:32   #14
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From what my lad has done its all pretty intense and expensive but he did motor yacht stuff up to 3,000 tons
Think up to press circa 18k cost wise
That sounds interesting, was it a career move?
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Old 30 November 2023, 19:26   #15
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That sounds interesting, was it a career move?
No hes done it from college started as a decky and worked his way up
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Old 01 December 2023, 12:41   #16
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No hes done it from college started as a decky and worked his way up
That's fantastic, dream job for me.
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Old 01 December 2023, 14:01   #17
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I agree it would have been interesting - I think it can be bloody hard work on the ships though - several of my buddies have spent long stints on the ships, one as engineer (working his way up through the grades) on large tankers, another doing oil exploration & drilling. It's a tough job.

And even if you're on a superyacht - if owner wants the yacht in a location at a specific date & time - you have to get there, regardless of the nasty storm you're just heading in to...

I've also heard that on the superyachts, it's important that you "see" absolutely nothing.

Anyway, just completed my ocean theory exam - fingers crossed I passed.
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Old 02 December 2023, 18:24   #18
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Yay! All passed. Right, what course next?
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Old 03 December 2023, 08:49   #19
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Well done. How much practical experience have you got? Have you seen the website where you can volunteer to crew on other peoples boats?
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Old 03 December 2023, 09:13   #20
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Spent most of the first half of my life on yachts. Will be a bit rusty, but how hard can it be.

Yeah, I've seen some of those sites, I'm in a facebook group too.

Next step is probably to pass my YM practical - will have to see if I can get enough hours logged to do offshore, otherwise will have to do coastal.

Also just downloading the forms to get HGV (C+E) provisional driving license - reckon being able to drive articulated lorries is a good thing, too.
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