Category: Celestial Navigation across the pond

Wednesday morning I cleaned out my cabin, packed my gear and said goodbye to the boat.  I walked back up to the sailing school arriving at 0900, “Come on in, sit down, here is the exam paper, you have 2 hours” the Examiner said to me cheerfully.  “Wow” I thought, this is the first hint of confirmation from another human being  that I might have actually got my head round this! 

I sat down and all my familiar friends were back around me, Almanac, plotter, dividers, plotting sheet.  I felt very comfortable, until I started to work through the paper.  I realised this was the first time I had worked through the calculation process without a pro-forma to copy from.  There was a brief moment of panic, but it was short lived.  My hand just started writing the figures down in the right order.  Of course!  Having done this repeatedly daily for the last month I really had learned it.  The answers flowed quickly, I’d finished with plenty of time to spare and handed the paper over to the Examiner.  

 

Next was a oral assessment, which was basically questions and answers about the trip.  How had I organised the watches, provisioning, routing, currents, weather patterns, ongoing maintenance, stores, power considerations etc etc.  The way the trip had panned out couldn’t have been better for me in many respects, since I genuinely had done and could prove all of the above.

 

 At the end of it the Examiner shook my hand and gave me a sealed envelope to post to the RYA once I got back to the UK.  I had successfully done it, sat and passed the RYA Yachtmaster Ocean exam!!  It turned out that 30 years ago the Examiner had also set off out into the Atlantic with sextant and instruction books and taught himself, thus he was suitably impressed with my efforts.

I had just enough time for a beer with my shipmates before the taxi arrived to take me to the airport.  Skipper was over the moon for me, having seen me drowning in a world of books and numbers, bordering on insanity for weeks. 

And that was that, airport and a couple of planes later I arrive home to a large bunch of flowers, a lit fire and a newly installed electric blanket!  I felt like I had just taken an exam and then had a really long bus journey home, so I insisted we drank Antigua Rum by the fire in the middle of this Thursday afternoon.

The 3 ton library had made it back home, I put my bags down and my thermals on.  

Today started at 0530, I plotted a quick EP to work out my LHA and GHA of Aries (me on the ocean compared to the Sheep on the dish) so I can go on deck and take a dawn star sight.  
I get sights on Arcturus, Spica, Sirius, Betelgeuse, Capella and I just miss Deneb before she vanished into the daylight (partly due to dropping a cup of tea all over the deck, I had to race for the kitchen roll before the boat rolled back to starboard sending tea down the steps and onto the deck below – I was too late!). 

It is too cloudy to see Polaris in the north, but I do see three satellites racing by. They sure shine bright in the early morning light, each one looked almost as big and bright as the ISS.  There was also an enormous falling star (possibly the 3rd biggest I’ve ever seen). 

In the east it is clear are two planets rising in the hazy of the breaking dawn.  The first one up I assume is Venus and the second Jupiter.  I take sights on them both since they are there, although the second one is probably too low in the sky to be useful.  

I have the 0600 to 0900 watch this morning, which is fabulous.  There is not a breath of wind out here this morning and the ocean smells kind of fishy or “ozone” as Dad calls it, that low tide smell at the breakwater, superb!  The sea is like glass, it is a beautiful morning and everyone else is in bed, so there is only me sat here to enjoy it.  Lovely! Thank goodness again for the catamaran and her large fuel tanks.  Luckily the forecast is suggesting 25 knots of breeze for us for the next few days, so hopefully we can sail the rest, if we can get this hotel up to 7 knots we’ll be there in 2 or 3 days….

 

As the sun rises I’m sat on the top deck doing my calculations on the sights I’ve just taken.  It turns out that this is the most accurate and beautiful star sight I have taken yet, all the lines cross almost at the same point, giving me a fix that I am totally confident of our position to within 5 miles (the thickness of the pencil cross on the ocean chart).  I love this, star navigation is my new favourite thing.

 

For good measure I elect to add the sight reduction from what I had assumed to be Venus, so I go through the calculations and get an answer that doesn’t make sense.  I know my LHA is correct, the star fix has proved that already, I check the GHA for Venus and declination – also correct.  After a few minutes of musing I put the same figures in but this time I use Jupiter instead of Venus and sure enough, the numbers add up.  In the week I have been off watch for dawn Jupiter and Venus have changed places in the sky.  This really is the icing on the cake for this morning’s fix, I really am starting to understand all this.

 

Shortly after 0900 a swallow lands on the rail on the port side.  The little guy was ready for a little rest, he must have been flying for some distance to be out here! He stayed with us for almost an hour, it was great watching him having a little clean of his feathers and keep his balance perched on a wire on this rocking boat.  I wanted to make a little bird bath for him, but figured I’d probably scare him off in the process.  Then he was gone, he is definitely winning the race to the Caribbean!

With not a zephyr of wind anywhere it sure was hot out on deck.  I’d not long retreated to the cool of my cabin when I heard loud voices, unusually loud.  I couldn’t work out what was going on, had they spotted or whale? It all sounded rather exciting, I headed for the deck.  The engine was off, the boat moving at less than half a knot.  The sounds I heard were coming from a couple of the crew swimming under the boat between the hulls.  It was the perfect day for it!

 

The sea is SOOOOOO blue today and very very very deep (5000m according to the chart).  400 miles away from land, here I am enjoying a cooling swim around the boat, certainly not your average November day!  Pleasant as it was I quickly began to feel like shark bait and was soon back on the boat. 

Out of the sea and straight into a hot shower – ha! This is living 🙂

 

 

The cool of my cabin was the best spot this afternoon.  I definitely have the best cabin, it is almost sound proof, there are no pumps or pipes running through it and being at the bow I get the breeze through three hatches, so it is the coolest place on the boat. 

 I force myself to wake up when I realise I am dreaming about Henry’s whisky!  Damn that bottle of Oban.  Just a wee dram would be such a treat, but I know one wee dram would rapidly lead to another….. And another…. And most likely another.

So I get up and set about working out my EP for this evening’s stars. Twilight and dinner seem to coincide exactly – again, so under pressure I shoot Vega, Fomalhaut, Deneb, and what I believe to be Nunki, but the numbers don’t add up, so I suspect I’ve got this one wrong.  Shooting stars in the evening is much trickier at least at dawn there is time to identify each star from its constellation before the dawn horizon comes in to view, as dusk I am still guessing somewhat.  Vega, Deneb and Fomalhaut I seem to have found, but the others are still a guess, so I don’t hold out much hope for a pretty fix like this morning’s one.  The Moon is also present in the western sky, just showing a sliver of a Cheshire cat smile, I take a sight on the Moon too for good measure, since I am only confident on three of my stars, a position line from the Moon might tidy things up a bit for me.

Now it is 2100, I have one more hour on watch, then up again at 0200 to 0600 and the chance to shoot the dawn twilight stars again. It is so still that Vega is actually putting a reflection on the sea.  

I’ve just seen lightning on our northern horizon, but since there isn’t a breath of wind it should stay away.  I don’t like thunder and lightning and I’m pretty confident that we are the tallest thing here for many many miles…..

 

 

It has taken me a fortnight to get to grips with sun run sun, Moon and planet sights.  I still have around 800 miles of the trip left to fathom star sights.  I’ve been shying away from this somewhat as the pro-forma given in Mr Cunliffe’s book is basically a page containing seven columns of numbers and it looks like a lot of heavy calculations.

 

My Favourite Book gives a list of 57 Stars, the brightest ones, thus they are the most useful to the navigator.  I learn that there are more we could use, but 57 seems like plenty to me.  I had been spoiled in the early part of the trip with a huge full Moon lighting up the horizon for hours.  The horizon is an essential part of sextant operation, through a clever series of sights and mirrors we can look at both a celestial body in the sky and the horizon in the same viewfinder, no horizon – no sights.  On these bright nights I took sights on everything and anything that I recognised, all of them featured on the list of “The 57 Stars”, thus I had assumed that I would be able to deduce my position from any or all of them at any time I could see them.  

 

Lesson number one, I need the horizon.  Lesson number two, taking sights on any random stars because you know their names, is not how this works!  It probably is possible,  I think the maths based book I had brought with me has all the right ingredients, but the language of cos, tan, sin, P, Z, X, and other Greek, was not one that I had ever learned or understood.  Throw in the added complication that we are not dealing with ordinary, regular straight edged triangles, no, our triangles have curved edges and this is all too much for my little brain.

 

I left the stars alone for a couple of weeks and focused my efforts on the Sun, Moon and planets.  Eventually I return to my best friends Mr Rodgers and Mr Cunliffe, they make a fix from the stars sound so simple and efficient, but the process looks so lengthy.  We must begin somewhere…

 

Aries, The First Point in Aries, to be precise, is where we start.  Already this couldn’t be straightforward, The First Point in Aries is just a point in the sky (more accurately a line of longitude on the celestial sphere).  

 

Aries…. Longitude…. Celestial sphere…. Confused already?  Yes, me too.  It gets easier when you realise that it is all just painted on a dish and most importantly that dish is spinning around us.  On that dish there are paintings, a sheep, a cow, a giant and his dog, then a unicorn, a pair of twins, a serpent, a lion and more, all locked in an eternal conga across the heavens.

 

As the dish spins around us we see the sheep pop its head up over the eastern horizon, over the course of the night the sheep will rise up, pass above our head and then descend in the western sky, the last thing we see is its tail dipping below the western horizon.  The cow follows the sheep, the giant is chasing the cow and the giant’s dog faithfully runs after the giant…. All night…. Every night…. Since long before we were around to observe them.

 

Back to the Point of Aries.  The point is this is our sheep.  The sheep passes exactly overhead at Greenwich in London at known (but slightly different) time each day.  The Favourite Book gives us “Sheep o’clock” for every day of the year, so that part is straightforward.  Provided I remember to read the “Sheep” column in the book of numbers, and not the “Sun” or “Moon” or one of the other numerous options given there.

 

Now, if I were at Greenwich, at Sheep o’clock, I would go to my new found friend The Stars Epoch book, find the page for my latitude, find the section for Sheep o’clock and the book will give me a list of seven stars.  If I use these seven stars to take my sights I can compare my sights directly to the numbers given in the Stars Epoch and from that I can work out where I am.  Once the correct numbers are there, the mathematical process is along the same lines as for Sun, Moon and Planets.  Seven stars and seven sights looks and sounds like a long and literally numerous task.

 

The next consideration is that I am not standing at Greenwich at Sheep o’clock, I am quite a long way west of Greenwich (two time zones different), so the sheep will pass over Greenwich two hours before it passes over me.  After all, they are just pictures painted on a dish, luckily the dish spins at a nice constant speed and the pictures are always the same distance apart.  If I’m standing in Greenwich looking at a sheep over my head, someone in Estonia would be looking directly up at, say, the unicorn.  

 

We know for certain that in a particular position, at a precise time the angles between the seven stars and us the observer, would match those angles given in the book.  Essentially from our estimated position we assume we are at a nice round number latitude and longitude that is nice and close to our estimated position.  We work out whether it is sheep, cow, giant, dog, or other o’clock with us and refer to the Stars Epoch book, to find the seven stars to use.  I frequently end up repeating this process, mostly through my own mathematical ineptitude, but practice makes perfect, so they say.  Next step is to go and find those seven stars, then wave the sextant at them, write the numbers down, do the maths and hope for the best.

 

Under the brightness of the moonlight, with the horizon visible this is feasible for many hours during the night.  But the full moon soon wanes and the nights get darker and darker as the weeks pass by.  The challenge now is that there are only two very brief times of day where both the stars and the horizon are visible together, the twilight at dawn and at dusk.  Now we need to know whether it will sheep, cow, giant, dog or something else o’clock during the short twilight spells.

 

I quickly learn lesson number three, prior preparation is essential before attempting star sights.  Then I come up against lesson number four when I discover that taking star sights at twilight is a constant race against the rising sun or the growing darkness each day.  There is no pause button, the dish keeps on turning.

 

I find it easier to take the morning sights.  Once the pre planning is done below deck, I get my head outside into the night while it is still nice a dark and all the stars are out.  There is time to sit on deck, stare at the pictures on the dish that is the sky and find the seven stars listed in the book, for my present time – Lion o’clock.  As the dawn starts to break and the horizon appears it doesn’t take long to get the stars lined up in the sextant, down to the horizon and the numbers recorded quickly.  

 

At dusk twilight, things are a little trickier.  I have been through the pre-planning, found which seven stars I should use for my local hour angle (which today is Fish o’clock).  Next  I need to shoot them before I lose the horizon to darkness, the race is on.  

 

To make matters more complicated I only know and recognise two of the seven stars and I have no other stars to use as reference, they are not out yet.  The seven listed stars are bright and so should appear first, but of course more than seven appear at the same time.  To solve this the Stars Epoch does give a bearing to each of the seven stars and a very good idea of roughly what angle above the horizon it should be.  So now armed with hand bearing compass, sextant and Star Pocket I search for my stars.

 

Vega is the first to show herself in the north west followed by Deneb in Cygnus.  Now for the others I don’t recognise, I manage to find Altair in Alquila and Fomalhaut (not sure which constellation). The weather is now working with the nightfall to thwart my plans and the stars in need in the east are lost in clouds.

 

It transpires that the daunting page of several columns of numbers is actually not as daunting as it first appeared.  Having followed the practical instructions of Mr Rodgers this far, I go to the pro-forma given by Mr Cunliffe, and copy his method with my numbers, I begin to see the simplicity of this final part.  We have been through all the complicated bits to reach this point, it is all downhill from here.  With numbers transferred to their corresponding columns, index error, height of eye and corrections all applied we are left with that magic number “Ho” for each star.  The mantra Ho Mo To returns again.  

 

The numbers lead a dance and again this mathematical pattern is trying to appear in the periphery of my mind.  I can’t see it and I doubt I ever will, it is far too complex for my little mind.  But I can see when my numbers look right and when they look wrong, dare I say it is starting to make sense.   

 

The final step is to draw the results on a Plotting Sheet and unlike Sun navigation which needs around four hours to produce three lines on a sheet, star plotting is a dream.  In one hour the sights are taken, calculated and there on the Plotting Sheet you have a position, with up to seven lines!  Our position is there, staring me in the face, that small triangle where most of the lines cross.  This whole process is super satisfying, I am totally confident that fix I proudly mark on the chart is where we are to within the thickness of a pencil line.

 

Occasionally on the Plotting Sheet I have a line which looks a long way off, I accept this human error. The stars all look pretty similar and I am battling the spinning of the dish, clouds and my sextant, with the useless telescope eyepiece removed and having to work the whole thing backwards.  I am not surprised that I lose a star every now and then.  Of course by now it is too dark or too light to go and take another sight, the dish has moved on, so have we, I can only accept the error for what it is and move on too.

I was woken just before my 0400 watch by the sound of something small and metallic, like a shackle or pin landing on the deck above my head.  Our skipper  checks the foredeck and confirms both of our suspicions.  There is a nut and washer on the deck and  the pin (a large bolt) that holds the boom to the gooseneck is starting to work its way up and out.  Luckily (in some ways) the pressure on the now angled pin has caused it to bend, so it wasn’t going to fall out easily, however, it also doesn’t want to go back in too easily either.  A few sharp smacks with a 6lb diving weight seems to do the trick.  The tack of the sail also sits through a ring at the head of this bolt, but there is no way we’re going to get it back through there now, so, in true resourceful style the tack is now being held down to the gooseneck with a sail tie.  Job all done just before day break.

Every degree travelled in a westerly direction equates to 4 minutes of time, so sunrise and sunset get later and later, so as sunrise approaches 7am and sunset approaches 7pm we know we are approaching a new time zone.  So now at 45 degrees west the clocks have gone back an hour and thus the sun rises an hour earlier.  So this morning I have the 0400 – 0600 watch with twilight now included.  

Today I am organised and prepared to take my star sight once the horizon becomes visible with the daylight.  This time I’ve worked out from the book which stars I should be using and I am successful in shooting five of them plus Polaris, but at dawn it is a bit of a race against the sun to get the job done before she rises and the stars all go to bed for the day, which is hopefully what I am going to do too.  It was a pretty morning, nice pink low sky with the crescent moon rising maybe an hour before the sun.

 

After 6 I’m off watch and before I go to bed I have a go at calculating and plotting the star sight, I am pretty successful this time round and come up with a reasonable position for us.  The good news is the now I am navigating by the stars I don’t need to be up to measure the sun at 9am, noon and 3pm.  I’m not due back on watch again until 1500, so that is one big fat massive sleep I’m going to have!

 

However, I seem to have adjusted to 3 hours sleep patterns and sure enough I am awake at 10 ish, it is raining and cloudy – ideal, no need to rush out anywhere, duvet day it is.  I sleep again until lunch time, having yet more crazy lucid crazy dreams. 

 

So after a very lazy morning I surface on deck around 2pm, my cabin is on the starboard side, so at the moment I am north facing out of my window, it has been cloudy through that view all day.  Out on deck it is glorious sunshine on the port side “Different day out here!” I remark.  I am totally sold on the star nav now, the math and the process is pretty simple and you get a nice accurate fix in one hit rather than the sun run sun process which involves three hits and three calculations, so by around 4pm you can tell where you were at noon!

 

The afternoon gave another uneventful watch, however we are now sailing!  And the news just keeps getting better, the wind has filled from the SE, which is unusual and unexpected, so finally we have the apparent wind on the beam and we are actually aiming at Antigua under sail for the first time on the whole trip!  The breeze holds until evening then becomes light and fickle again, so we are back to quietly motoring our way through a very very dark night.

 

At dusk twilight I have been through the star sight process again, pre planned which stars are available for my local hour angle and done my best to shoot them before I lose the horizon to darkness, so yet again the race is on.  This time is a bit trickier, only two of my seven stars I actually know where they are in the sky, so with hand bearing compass, sextant and star pocket I search for my stars.  They are all bright, so they appear early in the twilight, Vega is the first one to show herself.  I manage to find Vega in the constellation of Lyra, Deneb in Cygnus, Altair in Alquila and Fomalhaut (not sure which constellation), it is cloudy to the north and east, so I shoot what I think is Polaris, but when I do the math at the end it doesn’t fit, so I’m guessing that one was Kochab instead.  Half an hour of effort and I have a nice tidy fix plotted on my chart, happy!

 

 

I’m now fairly confident that I have got the hang of  sun sight reduction, sun run sun plots, moon and planet sights and have some beautiful fixes on my plotting sheets, a couple of Sun positions I am super proud of, a lovely fix using Venus and Polaris and another using the Sun and Moon since they were both up at the same time.  It is so rewarding when the sums all work out and I get a position which is mighty close to where we are.

Shipboard life goes in a constant rotation, the watches rotate every four hours at night, and once per person during the day, days and nights merge together, concept of day and date is only relevant for navigation.  The world keeps turning, which means the sky keeps turning, the sun and moon are set in their rotations, the earth is spinning around her axis, while she wobbles on it too and slowly declines south with each day that passes.  

I have literally spent most of the trip watching the world spin round through the eye-piece of my sextant and measuring her movements as she goes. It is a wonderfully satisfying experience when it all comes together.  

 

Every time I go on deck and stare at the ocean, or the sky or the stars, I think of Columbus, Magellan, Bligh, Cook, Worsley, Shackleton, and all the sailors of old whose view would have been exactly the same as mine is now.  The celestial bodies haven’t changed much, neither has that horizon.  

Although even in this great wilderness man has left his great legacy.  The sailors of generations gone before would have seen more marine life and no plastic in the ocean.

 

 

After 8 days of frantically scribbling numbers into my notebook varying amounts of light I now had a lot to catch up.  Having finally understood sun sight reduction it was time to get to grips with the Moon, planets and the stars.  My quest now, whilst maintaining my sun-run-sun routine, is to work through all the sights taken so far and get them plotted on the chart.  We are at least solar navigating now.   I will have nailed this by the end of the trip.  1730 and that is enough of the books, this would be my routine for a while.

 

It transpires that on our first night at sea I had taken what would prove to be a lovely fix using the Moon and Polaris (North Star).  The calculations for the Moon are only moderately more complex that those for sun sight reduction, thus equipped with Favourite Books 1 and 2 and following Mr Cunliffe’s step by step instructions we soon have a position line from the Moon.

 

Polaris hangs in the low northern sky and is the central point above which the heavens rotate above our heads.  This wonderful lady is the tail of Ursa Minor, or the Little Dipper and easily identified when Ursa Major (The Plough or the Big Dipper) rises, the bright stars in the “handle” of the plough point unmistakably at Polaris and continue to point at her all through the night, the centuries, the eons.

 

While the Sun only lunches once per day at noon, Polaris is at lunch all night, so we can ascertain our latitude from her at any time our horizon is visible, which with a bright full Moon could be all night.  The calculation for accurate latitude from Polaris turns out to be an incredibly simple.  We go through the routine outlined in the book, apply the numbers correctly and bingo we have our latitude.  The calculation itself is basically add a degree and a bit, add a bit, add a bit more and then subtract one degree, which effectively means that even without applying any corrections to the sextant sight Polaris should give your latitude to within half a degree (or 30 miles).  And with that I have two lines on a plotting sheet which cross at our position – YES!!  Lovely.

 

And now I see how Columbus discovered compass variation as he crossed the Atlantic.   It has baffled me for years how sailors could have known about magnetic variation, whose rate of change would be tiny on a daily basis on board a ship.  But of course, with Polaris hanging in the sky like the true North Pole’s lighthouse beaming out a light saying “north is here” sailors would quickly notice that their compasses didn’t point north.  

 

When “crossing the pond” changes in variation become more apparent.  On the eastern side our variation was around 8 degrees west, now more than half way across our variation is up to 13 degrees west and will keep rising as we travel toward the Caribbean.  There must have been some clever minds back then to notice this phenomenon, to work out what it is and to calculate it.  Once again my brain explodes at it all.  

I’d read about Plotting Sheets briefly on the online course and while the three instruction books I had on board each touched on the plotting sheet, there seemed to be some assumed knowledge here that I didn’t have.  The idiot me could not find a basic step by step instruction guide.  The sheets themselves did come with some basic instruction, but it didn’t quite fit with what I was trying to achieve.

 

It turned out that the huge gaping hole in my knowledge was transferred position lines, yes I must confess I thus far in my maritime career and never used or even thought about transferred position lines.  

 

I hear the navigators among you despairing, and trust me I was despairing for days, how could something that I felt sure was so simple elude me for so long.  At this point we have been at sea for eight days and I had done nothing but study and keep my watches of course, but even my night watches I spent more time staring at Sky TV than the empty horizon, I was possibly going slightly mad at this point.

 

Back to that infernal question “where on that line are we?” Finally the answer comes to me in the only really valuable bit of online course printing I’d done.  And there it is in black and white staring at me on the page “We move our estimated position to the closest point of the position line”.  Of course, of course, of course we do, of course it was so simple too.

 

Now I see, move the morning EP to the morning position line, draw our noon latitude on the plotting sheet, draw our track from the morning EP, move our position line down our track taking distance run from the log…. And there is it… the position line meets the noon latitude line and bingo, we have an actual fix which compares closely to where we are!!

 

To give real confirmation of this fix I can take an afternoon sun sight, again more maths, graphs, tables and calculations and I get another sensible position line on the plotting sheet.  I then move this back up the course line by the estimated 20 miles travelled and hey presto I now have a cocked hat triangle which puts us within 5 miles of GPS in latitude and longitude at noon.  Admittedly it is now around 1700, but it seems my days of despair and torment are over I finally have cracked this – YES!!!! I have been eight days at sea now, thinking of little else.   And there is it, a curtain has lifted and I see how simple the concept actually is, once you cut through all the jargon and endless books of numbers the process is pretty straightforward and with practice can only get easier.

This was the chapter I didn’t quite get to on the online course, so now I’m counting on having brought the right books, Google or Youtube tutorials are not available out here.  I found it a little frustrating that I’d paid for an online theory course, but hadn’t considered that there was no option to download the course, so, with the exception of a few pages I’d printed, I had no access to any of it whilst at sea, but I guess most people do the theory course first.

 

And now I’m about to get fully acquainted with new favourite book number two, this book only contains numbers, lots and lots of them.  I like this book, I can see when I have the answer right or wrong even though I can’t always see why at this point, but I can see that the numbers either “fit” or they don’t.  

 

This book enables us to refine our estimated position using the Sun, Moon and planets at any time of day or night.  Part of my morning routine, as per the instruction books, has been to take a morning sight on the Sun.  I’m at roughly 20 degrees north, it is November and I quickly observe how fast we are spinning as the Sun rises above the horizon at a fair old rate and every observation requires some twiddling of knobs on the sextant to keep the sun on the horizon.  At this time of day we take a series of five sights, record each one to the second and then head for shade.  

 

I’m also going through the same process with the afternoon to try and use sight reduction to ascertain a position line.  I seem to be able to collect the information I need from the sextant and use the sight reduction tables, but the logic of how the plotting sheets work is elluding me, the more I look, the more lines I draw and rub out and draw again the less it makes sense.  But I’ll keep trying, it will click eventually.  Until that happens the whole thing is driving me a little mad and without Google, Youtube or another human being to explain it to me it could be a very long learning process.

 

The next step is quite lengthy when you’re as mathematically inept as I am.  We need to work out the average of the five sights, “add them all together and divide by five” I hear you say, neither my brain or my calculator can cope with adding up three columns of degrees, minutes and seconds, all of which are 60s.  I am a metric girl, I was brought up with tens in columns, not sixties.  

 

So for each morning (and afternoon) Sun sight I draw a graph. As a result I think I am the inventor of “Navigators Graph Paper” where the squares are divided into sixes instead of tens.  We do this to come up with a number and average of our five sights, this is the angle we have measured between our horizon and the Sun, applied some corrections and written down as “Ho”.  This is where the real excitement begins, this is where I find out if I have correctly estimated our longitude, latitude and local hour angle and correctly observed the Sun.  If all of these things are correct the number I have (Ho) should be very close to the number I will obtain from Favourite Book number 2.  “Ho Mo To” has been the mantra my shipmate has been whispering for the last few days.  It turns out that once upon a time he had taken celestial navigation classes and this phrase was drilled into them.  “Ho Mo To” will mean nothing to you, but it meant the world to me once the penny dropped.  Seeing the numbers align themselves on the page is an immensely satisfying process, especially for the mathematically challenged, and a welcome confirmation that all of the above are good.

 

Rather disappointingly after all this the best we get is a line on a chart, all we know is that at the time the sight was taken we are somewhere on this line.  “But where?” That infernal question again… “somewhere on that line” is very vague, especially when the line is very very long.  I still feel rather lost in all of this!

 

I know the next thing I must do is work out what time I think noon will be, take our noon sight and with any luck, finally get my head round the mystery of the Plotting Sheet…

With the quest for noon latitude only allowing for one attempt per day I had been filling the hours taking morning and afternoon sun sights and observations on other celestial bodies, the Moon, Venus, Polaris and a whole host of stars, but I had very little idea what I was to do with all this data.  

 

It is our third night at sea and I have the 0000 to 0400 watch.  I go out on deck to a brilliant 99% full Moon.  It is so light out here it could be noon on a mid winter day at home, you could almost read a book out here.  The moonlight makes the horizon is clearly visible, so, (unusually I will soon learn)  in the middle of the night I have a go at trying to get some star sights with the sextant.  

 

I’m using a plastic cheapy sextant which is ok, but the telescope is not good enough to pick out the stars.  However, since I can see them with the naked eye I try taking the telescope off the sextant and just looking through the space left by the telescope.  To make this work I have to set the sextant to 0 and point the whole thing at the star until I have the star in the mirror, then I slowly work everything down to the horizon keeping the star in the mirror all the time.  It is tricky and my approach is the reverse of the recommended method described in the books, but it is the best I can do and it is working.  I have also been fortunate to grow up on an Island with “Dark Skies” status so I have already spent years learning my way round the constellations and stars, this is also helpful now I have resorted to this backwards approach.

 

“Star men do it with their eyes open” the book says and sure enough, no telescope, plenty of moonlight, a clear horizon and I am bring stars down to the horizon and getting readings!  Now I have so much information I’m struggling to sit down and face making sense of it all.  In the end I call this a sextant learning exercise and leave the maths for later.  The Sun is occupying all of my mental processing ability, there isn’t room for any more numbers right now.

 

The sextant and the celestial bodies are fast becoming an obsession and for days I took sights on everything and anything that I recognised.   Writing down endless numbers I pondered in awe about it all, a slow moving pattern is emerging.  

It turns out that during the day a sailor has only one real chance at confirming the ship’s latitude, this happens at noon each day.  When the Sun is at her highest point in the sky we can take our sextant, measure the angle between the Sun and the horizon and after applying some maths we can calculate our latitude.  

 

It also turns out that noon is not at noon, so already the whole affair becomes a little more complicated. This is where my new favourite book to be, The Admiralty Almanac, shows me exactly why it carries the hefty price tag, all the answers are in this book, I’ve just got to decode it.  Mr Rodgers and Mr Cunliffe provide sufficient guidance and I’m away.  Even standing still the time of noon varies by up to 16 minutes away from clock noon over the course of a year, because of something called the Equation of Time.  

 

The beauty of the navigation side to this is that you don’t need to know why this is, one simply needs to know where to look in the new Favourite Book.  Today noon is actually at 1144 if you’re standing on the Greenwich Meridian, which of course we are not. .  So… I know the Sun will pass over Greenwich in London at 1144, from my dead reckoning position I have an idea of how far west we are, so the Sun will pass over my head some time after 1144.  I can now refer to the favourite book and estimate what time the Sun should reach her highest as she passes over my head (or my meridian on the globe if you prefer).  

 

Then it is off out on deck in the heat of the midday sun, armed with sextant, watch, notebook and pencil.  First thing, check and write down that sextant error bit, once that is done it is time to start watching the world spin round using a small telescope and a couple of mirrors.  I am on deck 20 minutes before I expect my local noon to happen (since mine is only approximate based on my estimated position), and so I measure and watch as the sun stops rising in the sky, now she seems to steady on the horizon for a few minutes before she begins her slow descent toward the western horizon.  And that is it, it is all over, we have our time and measurement taken with the sextant written down and it is time to get back into the shade.

 

Now I am getting more acquainted with my new Favourite Book, it will help me do a handful of calculations to (hopefully) ascertain our latitude at noon.  Two important things happen here.  First off the world tilts on its north south axis, hence we get longer days and the sun higher in the sky during the summer and now, in the winter our days are short and the sun is low in the sky.  In the celestial navigation world this is called declination. And that, is more than we need to know about it, we’ve just got to ask the Favourite Book for the answer.  We do however have to ask it the right questions, mostly “what time is it at Greenwich” and “what time is it with me here and now”, the book reveals differences between the two that we must take into account to find our precise declination.  Then a very quick sum and we have our latitude.

 

At this point I don’t think it is cheating to now check our noon position according to the GPS to see if I am close or not.   In a beginners kind of way I probably am close, on the scale of the ocean chart it looks close, but for the first three days my noon sights were not accurate enough.  

 

I continued this process like a devoted student, on day three I realise the error I have is a consistent one, so this time I take the noon latitude from the GPS and do the maths backwards to work out my errors.  Operator error and operator understanding are definitely the cause, looking at the sextant instructions on or before day one would have been an idea too.  So with errors found and corrected and corrections applied to the previous sights too, my latitudes are now acceptably close to our GPS track and I am starting feel that the task I have set myself might still be achievable..