Buoyage — At night, and on the chart

Reading notes · Buoyage

The rhythm of every mark, the cardinals' three-six-nine clock, and how the chart writes it next to the buoy.

Open the interactive chapter →The same material with the chart, the drawings and the exercises.

Reading a rhythm · topic 1

Two of the three are gone

This is the port-hand mark you have known since part one. On the left it is daylight: a red can, flat on top, and you have it in one look.

On the right it is the same buoy at night. The shape has gone and the colour has gone — a light has no shape, and at any distance your eye is poor at colour. Two of the three things that identify it are simply not there.

What is left is the one thing daylight never showed you: the rhythm. Watch it. It is running in real time — nothing here is sped up — and that pattern is what tells you which buoy you are looking at.

A rhythm shown here is an example, not a rule. A lateral mark may flash any way at all except the compound group — that one belongs to the preferred-channel marks — and a special mark may flash any way at all. What identifies those two is the colour, not the period. You will meet four laterals in one channel later in this part, and no two of them flash alike. The other marks are not like that: a cardinal, a preferred channel, an isolated danger and a safe water each have a rhythm that is theirs and nobody else’s.

Everything in this part is that pattern: how to read it, how to write it, and what each mark's own rhythm is.

A light is a rhythm

At night a lighthouse is not a symbol on a chart. It is a light that comes and goes, and the pattern it makes in time is the only thing that tells you which light it is. Two lights on the same coast can look identical. Their rhythms cannot.

The chart writes that rhythm as a character: one or two letters. Seven of them cover almost everything you will meet.

Fl is darkness interrupted by light. Oc is light interrupted by darkness. You do not have to remember which is which — look at which there is more of.

Groups, period, colour

One flash on its own is not much to go on. A coast can have several lights all flashing, so flashes come in groups, and the group is written in brackets after the character.

The number in the brackets is how many flashes are in one group, and nothing else. It is not seconds. It is not a range. It is a count.

Then comes the number with the s on the end. That is the period: how long one whole cycle takes, from the start of one group to the start of the next. The darkness counts.

And the period is the one part you can measure yourself. Start a watch on the first flash of a group, stop it on the first flash of the next. Whatever it reads is the period.

One last piece: the colour. White, red, green or yellow, and the letter goes after the character and its group, before the period. If no colour is printed, the light is white.

Every mark you met in part one has a rhythm of its own. The South cardinal — the one whose cones point down — flashes in a way you can now read: a character, a group, a period. What that particular group means, and why it is six and not five, is the next topic.

You can read a light now

This is the light you were shown at the start of this part, when all you could say about it was that it came and went. Now you can write it down.

Flashing. No group. Red. Five seconds. Four readings, and none of them helps you with the others: the proportion gives you the character, counting gives you the group, your eyes give you the colour, and only a watch gives you the period.

What you cannot do yet is say what it means. A rhythm read is a rhythm and nothing more. From here on every rhythm you meet is attached to a mark, and the mark is what you actually need at two in the morning.

The cardinals go first, because theirs is not a signature to memorise — it is a clock.

The cardinals' clock · topic 2

Four buoys, four white lights

These are the four cardinals — the ones whose cones you learned to read in part one. At night this is all you get.

All four are white and all four are quick. No colour to separate them, no shape, no topmark. If the light were the only thing you had, three of these four would put you on the wrong side of a rock.

But they are not the same, and the difference is one you can count. Watch them a moment before you go on: one of them never stops, and the other three come in bursts of different lengths.

There is a reason those bursts are the lengths they are, and it is the neatest thing in this whole module. That is the next screen.

Move it yourself

Tap an hour. The hand goes to it, and the light beside it changes to match — count the flashes and you will find the hour you just tapped.

The clock does not move. You do. The number on the face and the number of flashes are the same number, and once you have seen that a few times you will not need the clock again.

Try twelve last. There is no hand, because there is no number — and that is exactly what its light does.

Nothing is scored here.

The other eight, after dark · topic 3

And now the colour is back

The four cardinals were all white, and you separated them by counting. The other eight are not. Red, green, white, white, yellow, red again, green again — and one that will not hold still.

Colour looks like the easy answer, and it is the one you cannot lean on. At two miles, in rain, with a town lit up behind it, a red light and a green light are a light. And there are two reds and two greens here anyway, so even seeing the colour leaves you with a pair.

So take the rhythm first and the colour second. Count the flashes and time the long ones; the colour is what confirms it, not what decides it.

Which is which is the next screen — and the two whites are the pair worth being certain about.

Which is which

Now with their names on. Read each one the way you learned in topic one: character, group, colour, period — every one of these is written the way the chart writes it.

The two plain laterals are one flash each, and only the colour separates them. The two preferred-channel marks are the same pair again — red and green — and what separates them from the plain ones is the group: two flashes and then one, which is that mark's signature and belongs to nothing else.

The special is the only steady yellow in the system, and the new danger is the only light that changes colour on you: blue, yellow, blue, yellow. If a light will not settle on a colour, that is what it is.

And the two whites are the pair that matters. Safe water gives one LONG flash — two seconds or more, slow enough to feel slow. Isolated danger gives two short ones, and only ever two.

Confuse those two and you take a danger for open water. It is the worst mistake in this module, and the rhythm is what stops you making it.

How the chart writes it · topic 4

The same buoy, written down

Three views of one buoy. On the left the object, in daylight. In the middle the light, after dark — you have spent this whole part learning to read that. On the right, what the chart prints beside it.

The magenta flare means «this one is lit». It is not the light and it is not to scale: it is a flag saying there is something here to see at night. The little circle at its foot is the position — that part is exact, and it is the only part that is.

And beside the flare, the characteristic: the same four pieces you learned to write in topic one. Nothing new to learn — it is the middle picture, in words.

Read it and you know what to look for before you ever leave the berth. That is the whole reason the chart bothers to print it.

And when the chart says nothing

This is a South cardinal on your chart, and you know what a South cardinal’s light is by now: six quick flashes and a long one. But look at the paper.

There is no flare and there is no characteristic. The chart is not being lazy — it is telling you something exact: this buoy is not lit.

If there is nothing printed, do not expect to see it at night. It is there, it is on the chart, and in the dark you will go past it without knowing. Everything you learned about the cardinals’ clock applies to the lit ones — and on this chart, the lit ones are the channel.

That is worth checking before you plan a night entry: not «what does this one flash», but «does it flash at all».

Going in after dark · topic 5

The same channel, at two in the morning

This is Stennick Haven — the channel you took apart in part two, mark by mark. This is what is left of it after dark.

No shapes, no colours you can trust at this distance, no names painted on anything. Six lights on black water, and you have to know which is which before you commit to going in.

Everything you need is there. One of them is white and slow — that is the doorway. The rest come in pairs, and the pairs are what the next screen is about.

Watch it for a moment. They are all running on the same clock.

Two greens and two reds

With their names and their characteristics on. Look at what the colour does and does not tell you.

Colour tells you which side of the channel a buoy marks — red one edge, green the other, and going in with the arrow you know which hand to leave each on. That much you had in part two.

But there are two greens and two reds, and the colour cannot tell them apart. Both greens are green. Both reds are red. What separates them is the period: five seconds for the first pair, six for the second.

That is what the period is for, and it is why the chart bothers to print it. Colour tells you which side. The period tells you how far in you are.

What you can do now

Twelve marks, lit. You now have all three sides of every one of them: what it is, which side you pass it, and what it does after dark.

A light is a rhythm, and a rhythm is four things. Character, group, colour, period. Three of them you can see at a glance. The fourth you have to time — and it is the one that separates two lights flashing the same way on the same side of the same channel.

The cardinals run on a clock. Three, six, nine, and north which has no number and so never stops. The long flash on the south is there for one reason: so that a six counted in a seaway cannot pass for a three or a nine.

And the chart says all of it before you leave the berth. A magenta flare and four pieces of shorthand beside the buoy — or nothing at all, which is itself an answer: that one is not lit, and after dark it is not there.

What you cannot do yet is turn any of this into a position. Seeing a mark and knowing where you are from it are two different skills, and the second one is what comes next.

Open the interactive chapter →The same material with the chart, the drawings and the exercises.

All the reading notes →