Night Sailing and Watchkeeping

Prerequisites

• RYA Competent Crew or equivalent, with at least 4 night hours on board a sailing yacht. This is part of the pre-course experience the RYA recommends for the Day Skipper Practical course, which itself includes an introduction to night cruising.
• Day Skipper lessons on COLREGs (navigation lights, Rules 5, 7, 8 and 13 to 19), IALA buoyage and light characteristics, pilotage and safety equipment. This lesson applies them in the dark and does not repeat the full rules.
• Ability to plot a position, take a bearing with a hand-bearing compass and work up an estimated position (EP).

Learning Objectives

By the end of this lesson you will be able to (RYA Day Skipper practical night cruising, and shorebased Collision regulations, Pilotage and Buoyage syllabus):

• Prepare the boat, the crew and the passage plan for sailing at night (RYA syllabus: night cruising, preparation).
• Explain how night vision works and how to protect it.
• Organise a watch system, conduct a structured watch handover and manage fatigue.
• Keep a proper lookout at night and identify vessels by their lights (COLREGs Rule 5 and Part C).
• Use the bearing of a light to judge risk of collision and take early, clear avoiding action.
• Navigate and pilot at night using lights, sector lights, leading lights and the echo sounder.
• Prepare the crew and the boat for emergencies after dark.
• Calculate the range at which a light is first seen (nominal, luminous and geographic range) and use a rising light as a check.
• Plan and make a night entry into an unfamiliar harbour, with an abort plan.

RYA Syllabus Map

What the examiner expects. On the night element of the practical course the instructor will ask you to identify lights and their characteristics, to say which way a vessel is heading from her lights, to take bearings of a vessel and state whether risk of collision exists, and to organise the crew's watches. They are looking for red light discipline, a lookout kept all-round (including astern), and a skipper who briefs the watch and who is called early.

Why Night Sailing Is Different

At night the same boat, the same sea and the same rules become harder for three reasons:

1. Less information. You see points of light, not shapes. Distance is very hard to judge. A small fishing boat close by and a large ship far away can look much the same. Unlit objects (pot buoys, moored boats, logs) are invisible.
2. Slower human performance. Your eyes need time to adapt, colour vision fades, and the body's natural sleep cycle pushes you toward drowsiness between about 0200 and 0600.
3. Harder emergencies. A man overboard or a fire is far more difficult to manage in the dark.

The answer is preparation, light discipline, a proper watch system and a deliberate lookout. Done well, night sailing is calm and rewarding, and often the best way to cover distance or catch a tide.

Preparing for a Night Passage

Passage plan

Prepare night-specific notes for each leg in your pilotage plan:

• Every light you expect to see: lighthouses, buoys, leading lights and sector lights, with characteristics, ranges, and the bearing and time at which they should appear (rising or dipping distance for major lights).
• Clearing bearings and sector boundaries that keep you off dangers.
• Depth contours you can follow (see below).
• Shipping lanes and ferry routes you will cross, and fishing areas.
• Ports of refuge that can be entered at night, and those that cannot.
• Times of sunset, end of civil twilight, moonrise and sunrise.

Write the notes large enough to read under a dim light, or put them in a waterproof cockpit notebook.

Boat

Before dark (ideally before you leave):

• Test the navigation lights: sidelights, sternlight, masthead or tricolour, steaming light, and the anchor light. Carry spare bulbs and fuses.
• Rig jackstays and check harness strong points in the cockpit.
• Put a torch in a known place for each watch, plus a powerful searchlight. Check the batteries.
• Fit lifejacket lights and personal AIS beacons and check they work.
• Reef before dark if there is any doubt. Reefing at night is slower and riskier.
• Stow loose gear, so everything is where people expect it.
• Prepare hot drinks and food in flasks, so cooking is minimal at night.
• Set dimmed red or white lighting below. Turn instrument displays to night mode.

Crew

Brief the crew in daylight: the watch rota, lifejacket and harness rules (both worn and clipped on at night), how to call the skipper, light discipline, how to report lights, and night MOB procedures. Get the off-watch crew to sleep early. People who start a night passage already tired are a liability.

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Night Vision

How the eye adapts

The retina has two kinds of light receptor. Cones, concentrated in the centre (the fovea), give sharp detail and colour vision but need good light. Rods, spread around the periphery, are very sensitive to dim light but see no colour. In the dark, the rods take over. They need the pigment rhodopsin, which builds up slowly over 20 to 30 minutes of darkness and is bleached in a moment by bright white light.

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Practical consequences:

• A person coming up from a bright cabin is nearly blind for the first several minutes. Don't hand them the helm in traffic straight away.
• One flash of a white torch or cabin light can wipe out the adaptation of everyone in the cockpit.
• Red light affects the rods much less, so it helps preserve night vision. But it destroys colour perception: red and magenta chart detail disappear under red light, and red buoy lights become hard to judge. Modern practice is to use very dim white at the chart table and keep red for moving around.
• Shout "white light coming on!" before switching on a white light, so people on deck can close one eye or look away.
• Older eyes adapt more slowly and less fully. Put your best night eyes on lookout.

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Seeing with your peripheral vision

Because rods are sparse in the fovea, a faint light can disappear when you look straight at it and reappear when you look slightly to one side. Look about 15 to 20 degrees off the object and scan slowly, pausing briefly at each point. Don't sweep the eyes continuously, because the eye detects objects mainly during the pauses.

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The Watch System

Why a formal rota

At night someone must always be keeping a proper lookout (COLREGs Rule 5) and steering, while others rest. If the arrangement is vague, either everyone stays up and the whole crew is exhausted by 0300, or there are gaps when no one is really watching.

Who is on deck

A sound standard on training yachts, and the one this lesson recommends, is at least two people on deck at night: one helming and one keeping a dedicated lookout and doing the navigation. They are clipped on, and each keeps an eye on the other. There is no law against a single watchkeeper, and a short-handed boat may have no choice, but in that case the lone watchkeeper must be clipped on at all times, wear an AIS MOB beacon, use the autopilot so they can look around properly, and wake the skipper if in any doubt.

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Common rotas

On a typical Day Skipper coastal night passage of 6 to 10 hours, two watches of two people doing 3 hours on and 3 hours off, with the skipper "floating" and available, is a good arrangement. The skipper should be called for any doubt about a light, a vessel, the weather or the position, and should never be annoyed at being called.

The watch handover

A handover is a transfer of situational awareness. Done badly, the new watch knows nothing about the ship coming up astern or the change of course due in 20 minutes.

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1. Call the incoming watch 15 minutes early, so they can dress, have a drink and let their eyes adapt in the dark companionway.
2. The outgoing watch briefs on: position and how it was fixed, course to steer and next waypoint with ETA, traffic in sight (bearings, whether they are changing), lights expected next, weather and barometer trend, sail plan, anything wrong with the boat, and any skipper's orders.
3. The incoming watch repeats back the critical points and looks around for itself.
4. The handover is explicit: "You have the watch." "I have the watch."
5. Log the time, position, course, speed, barometer and anything notable.

Fatigue

Fatigue builds unnoticed. It slows reaction time, narrows attention and dulls judgement. Worst of all, it causes microsleeps, blackouts of a few seconds of which the person is unaware. At 6 knots a 5-second microsleep covers 15 metres. The natural low point is roughly 0200 to 0600.

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Countermeasures:

• Rest before the passage, and make the off-watch crew sleep, not chat in the saloon.
• Keep warm and fed. Cold and hunger both accelerate fatigue.
• Caffeine helps, but takes 20 to 30 minutes to act. Drink it before the expected low point, not after.
• Keep moving and talking. Change helm and lookout within the watch every 30 to 60 minutes.
• Fresh air on the face. Avoid sitting in the warm, sheltered corner under the sprayhood.
• Admit it. A watchkeeper who says "I'm struggling" is acting responsibly. The skipper should make that easy to do.

Lookout and Collision Avoidance at Night

A systematic lookout

• Scan all round: ahead, both bows, both beams, and astern at regular intervals. Overtaking ships approach from behind, unseen, behind the sails.
• Look under the genoa to leeward. A low-cut headsail hides a large arc. Duck down or go to the leeward side regularly.
• Use your ears as well. Engines, breaking water on a rock, a bell or a fog signal.
• Report every light to the helmsman: "Light on the starboard bow, white, steady, bearing 045."
• Use AIS and radar if fitted, but remember that many small craft and fishing boats don't transmit AIS. A lookout by eye remains the legal and practical requirement.

Identifying vessels by their lights

The COLREGs lesson covers the rules in full. The key configurations to recognise quickly are:

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Lights at night are best identified by a protocol: (1) colour or colours, (2) arrangement (vertical, horizontal), (3) flashing or steady, (4) the bearing and how it is changing, and (5) the chart (is there a buoy or lighthouse there?).

Also look out for anchored vessels. Under 50 m, a vessel at anchor shows one all-round white light where it can best be seen. Vessels of 50 m and over show two, the forward one higher. Large anchored vessels may also light their decks. Your own boat must show an anchor light from sunset to sunrise when anchored (a vessel under 7 m is exempt when it is not in or near a narrow channel, fairway or anchorage, or where other vessels normally navigate).

Risk of collision at night

COLREGs Rule 7 states that risk of collision exists if the compass bearing of an approaching vessel does not appreciably change. At night this is your main tool, because you cannot judge course and distance by eye.

Procedure:

1. Take a bearing of the light with the hand-bearing compass (or line it up with a stanchion or shroud, keeping your head and the boat's course steady).
2. Take another bearing a minute or two later, and again after that.
3. Steady bearing and lights getting brighter or further apart (the masthead lights opening) means risk of collision.
4. A large ship at close range may show risk of collision even with a slowly changing bearing, because of her length.
5. If you are the give-way vessel, act early and substantially (Rule 16): for example, a 60-degree turn to starboard, so that the other vessel sees your lights change. At night this means she sees a different combination of your sidelights. Small alterations of 5 or 10 degrees are invisible.
6. Keep taking bearings after the alteration to confirm the bearing is now changing and the vessel will pass clear.
7. If in doubt about the other vessel's intentions, make the sound signal of at least five short blasts and illuminate your sails with a torch. You may also call on VHF Channel 16 or 13, but don't rely on a VHF conversation.

Remember that a sailing yacht's lights are small and low, and that from the bridge of a big ship they may be lost against shore lights or in the sea clutter. Assume you have not been seen. Shining a powerful torch on your mainsail makes a yacht much more visible.

Navigating at Night

Identifying lights

Use the method from the buoyage lesson: colour, count the flashes, time the period, compare with the chart. Lighthouses have long ranges and distinctive characteristics. On a clear night a major light appears over the horizon ("rising") at a predictable distance, which gives a good position line combined with a bearing.

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Shore lights make identification harder: streetlights, cars, houses and flashing shop signs. A navigation light has a regular, repeating rhythm and stays on the same bearing as you move. Shore lights don't.

Light ranges: when will I first see it?

Three ranges matter and the Admiralty List of Lights and the chart legend give them.

• Nominal range is the luminous range in a meteorological visibility of 10 nautical miles. It is the figure printed on the chart beside the light ("Fl(2)10s 25m 18M"). The light is visible at this range only if the visibility is 10 miles or better and the observer is high enough.
• Luminous range is the range at the actual visibility. In haze of 5 nautical miles a light of nominal range 18 M may only be seen at about 10 M. In fog it may be nothing.
• Geographic range is limited by the curve of the Earth. For a light of height H metres and an observer at height h metres, the geographic range in nautical miles is about 2.03 x (the square root of H plus the square root of h). The light appears over the horizon at the lesser of the geographic and luminous ranges.

Worked example. The light is 25 m high, nominal range 18 M, and your eye is 2 m above the sea. Geographic range = 2.03 x (5 + 1.41) = 13.0 M. Nominal range is 18 M, so in 10-mile visibility the light is first seen at 13.0 M (the geographic limit). In 4-mile visibility you would only see it at much less than 13 M. A quick rule: always compare the geographic and the luminous range, and expect the lower to be the true range.

Using a rising light as a position line. If you see the light just appear over the horizon, you are at about its geographic range, 13.0 M in the example. Draw a circle of radius 13 M around the light and your position is on it. Combined with a bearing this gives a fix that is only approximate. Treat it as a check, not a fix.

Dipping distance is the same idea in reverse: as you sail away, the light dips below the horizon at the same distance. Note the time.

Sector lights

A sector light shows different colours in different arcs. Typically a white sector marks the safe approach, with red and green sectors on either side over dangerous water. The chart shows the sectors and their limiting bearings, measured from seaward toward the light.

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• If you are in the white sector, you are in the safe channel. If the light turns red or green, you have strayed toward danger. The chart tells you which side.
• Sector boundaries are not knife-edged. There is a narrow zone, typically a degree or two, where the colours merge and the light can look pinkish or flicker between colours. Stay in the middle of the sector, not on its edge.
• Note that sometimes the colours are reversed, or a sector shows an intensified or obscured light. Always read the chart.

Leading lights

Two lights, one behind and higher than the other, show a line of safe water. When they are one above the other, you are on the line. If they separate horizontally, you have drifted off the line, and parallax tells you which way: the nearer, front light appears to shift more than the rear one.

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Correcting a leading line:

1. Look at the rear (higher) light relative to the front (lower) light.
2. If the rear light appears to the left of the front light, you are to the left of the line. Move right to get back on it.
3. If the rear light appears to the right of the front light, you are to the right of the line. Move left.
4. In short: the rear light shows the side you are on, so move toward the side of the front light until they stack again.

Check the alignment continuously. A tidal stream across the line will push you off it steadily, so you may need to steer a few degrees off the line's bearing to stay on it.

Depth as a night reference

The echo sounder works just as well at night. Plan to use it:

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• Set the shallow alarm to a safe depth (your draught plus a margin, corrected for the height of tide).
• Choose a depth contour to follow, such as the 10 m line along a coast. Steer to keep the soundings on it, correcting for the height of tide.
• Cross-check soundings with the chart at each fix. Distinctive features (a steep-sided channel or a bank) confirm your position.
• Unexpected shallowing means stop and verify your position before going any further.

Fixing at night

Fix more often at night than by day, because you have fewer visual checks between fixes. A three-light fix with a hand-bearing compass is quick and reliable if the lights are well spread. Compare it with GPS. Keep a log entry every hour at least, so that you could work up an EP if the electronics failed.

Entering an Unfamiliar Harbour at Night

Night entry is one of the hardest tasks in the Day Skipper practical, and the RYA instructor expects you to make a calm, prepared approach or to decide not to enter.

Before you arrive (1 to 2 hours out):

1. Complete the pilotage plan: every mark, light and leading line in order with characteristics, bearings and tidal depths. Write the plan on a card for the cockpit.
2. Check the harbour guide for restrictions: tidal gates, speed limits, signals, and especially whether there are unlit moorings, sandbanks or shoals marked only by unlit buoys.
3. Check the tide: depth at the entrance at your arrival time, and the stream across the entrance.
4. Brief the crew: positions (helm, navigator, bow lookout with torch, fender and warp crew), plus red torches only. Bring the sails down in a deep-water area outside and prepare to motor in.
5. Fix your position and identify the outer mark positively by its characteristic before committing.

Approach:

• Approach from a position you know. Use a leading line or sector light if there is one.
• Call out marks as they pass. The navigator checks each against the plan: "Green conical, Fl G 5s, to starboard, depth 6.4."
• Motor slowly. At 3 to 4 knots a mistake is recoverable.
• Shore lights confuse. Count flashes and time the period before deciding a light is a mark. If you cannot positively identify the entrance after two minutes, stop, keep clear of the shore and re-fix.
• Have an abort plan: where you will go if the entrance cannot be identified or the situation is worse than expected. Heave-to or anchor in safe water and wait for light. This is seamanship.

Berthing: choose a berth beforehand if possible. Visitors' berths at night often mean slow, quiet manoeuvring, because there is no one to take lines. Use headlamps with red filters and avoid shining torches in the eyes of other crews.

Worked Example: Collision Bearing

At 2230 you see a white masthead light and a green light, 30 degrees on your starboard bow. You are a sailing yacht heading 270 degrees Magnetic.

• 2230: bearing 300 Magnetic, estimated distance 3 M.
• 2233: bearing 300 Magnetic. The lights look brighter and the green light is more distinct.
• 2236: bearing 301 Magnetic. The red light is not visible, there is a second masthead light higher above the first.

The bearing has not changed appreciably. Risk of collision exists (Rule 7). The two masthead lights and the green sidelight show a power-driven vessel of 50 m or more, crossing from your starboard to your port and showing you her starboard side. She has you on her starboard side, so Rule 15 also makes her the give-way vessel. Because you are a sailing vessel and she is power-driven, Rule 18 makes her the give-way vessel and you the stand-on vessel (Rule 17). Keep your course and speed (Rule 17(a)(i)), sound five short blasts if you doubt she is taking action, and keep taking bearings. If she is clearly not keeping out of the way, Rule 17(a)(ii) lets you take avoiding action at once, and when collision cannot be avoided by her action alone, Rule 17(b) requires you to do whatever best avoids it. Slowing, starting the engine and making a large alteration to starboard to pass astern of her are the usual options. Tell the crew, record the event in the log, and consider shining a torch on the mainsail.

Night Emergencies

The safety equipment lesson covers the equipment, and the MOB lesson the recovery techniques. At night:

• Prevention is everything. Clipped on, lifejackets on with lights and AIS beacons, never alone on the foredeck.
• MOB: shout, point, throw the lifebuoy with its light and the dan buoy, press MOB on the plotter, and turn on the deck lights and searchlight. Send a DSC alert and Mayday early. The Coastguard would far rather stand down a search than start one late.
• Flooding is harder to hear over wave noise at night. Check the bilge on each watch.
• Fire: know where the extinguishers are well enough to find them in the dark.
• If conditions are beyond the crew at night, heave-to or anchor and wait for dawn if it is safe to do so. That is good seamanship, not timidity.
• Fog at night combines the two worst cases. The RYA checklist applies: fix your position, listen on the port channel and Channel 13 for shipping, hoist the radar reflector, sound the fog signal every two minutes and listen, crew on deck in lifejackets, keep an experienced radar watch if you have radar, get out of the shipping lanes and follow a depth contour or anchor in shallow water, and never aim straight for a harbour entrance: aim off to one side so that you know which way to turn and stay out of the path of commercial traffic.

Worked Example

A coastal night passage. You are skippering a 10 m yacht with three crew on a 40 nm passage, departing at 1900 to catch the tide round a headland at 0100.

1. 1800, alongside. You test the navigation lights, rig the jackstays, fit lifejacket lights and AIS beacons, put a torch by the companionway, and fill flasks. You brief everyone on the watch rota (you and Alex, Ben and Chris, 3 hours on and 3 off from 2100), clipping-on rules, light discipline and how to call you.
2. 1900, departure in twilight. Leading lights out of the harbour are easy to see in the dusk. The crew's eyes adapt gradually as the light fades.
3. 2130. Ben reports "a white light over another white light, with a green light below, fine on the port bow." Masthead lights in line, green sidelight: a power-driven vessel over 50 m, crossing from port to starboard. You take bearings: 330°M, 330°M, 331°M over three minutes. Effectively steady, and the lights are getting brighter. She is the give-way vessel (she has you on her starboard side), but you keep watching. After two more minutes the bearing is still steady and she has not altered, so you sound five short blasts and shine the torch on the mainsail, ready to take action under Rule 17 if needed. She alters to starboard and the bearing starts to draw aft.
4. 2200. Handover to Ben and Chris, 15 minutes early, with a full brief and repeat-back.
5. 0100, rounding the headland. You are called as planned. The lighthouse shows Fl(3)WR.15s. You are in the white sector. You keep the sector and the 20 m contour as your guide and stay in the middle of the white sector, well clear of the red boundary.
6. 0400, arrival. The approach is lit and you have planned it, but the crew is tired and the harbour unfamiliar. You decide to pick up a visitors' mooring outside and enter in daylight. That is a safe decision, not a weak one.

Common Mistakes

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• Bright white light from a cabin, torch or plotter at full brightness, destroying everyone's night vision.
• Staring directly at a faint light, then losing it.
• Not looking astern or under the genoa.
• Small course changes at night, which the other vessel cannot see.
• Hugging the edge of a sector.
• Relying on red light at the chart table and missing magenta and red chart detail.
• No formal watch system, so everyone is tired at once.
• A sloppy handover that leaves the new watch unaware of traffic or a planned course change.
• Pressing on into an unfamiliar harbour at night with a tired crew, when waiting for dawn was an option.
• Assuming you have been seen. A yacht's lights are small and easily lost against the shore.

Summary

• Prepare in daylight: lights tested, jackstays rigged, reef early, torches placed, food ready, crew briefed and rested.
• Night vision takes 20 to 30 minutes to build up and is lost instantly to white light. Use dim lighting, announce white light, and look slightly off-centre to see faint lights.
• Use a formal watch rota. Two on deck is the recommended standard. Hand over with 15 minutes' overlap, a full brief and repeat-back. Manage fatigue actively, especially from 0200 to 0600.
• Lookout all round, including astern and under the genoa. Identify vessels by their lights. Risk of collision exists when the bearing is steady: act early, boldly and visibly.
• Identify navigation lights by colour, flashes and period. Stay in the centre of sector lights. Keep leading lights in line. Use depth contours and frequent fixes.
• Clipped on, lifejacket lights and AIS beacons for everyone. If in doubt, wait for daylight.

Check Your Understanding

1. Why is red light helpful at night, and what is its main drawback at the chart table?

Answer: The rods, which give night vision, are much less sensitive to red light, so red light preserves dark adaptation. The drawback is that red light removes colour perception, so red and magenta chart features (light flares, sector colours, some dangers) become hard or impossible to see. Dim white light is better for chart work.

1. How long does full dark adaptation take, and what should you say before switching on a white light?

Answer: About 20 to 30 minutes. Warn everyone with "white light coming on!" so they can look away or shut one eye.

1. List six things the outgoing watch should brief at a handover.

Answer: Any six of: position and how it was fixed, course to steer, next waypoint and ETA, traffic in sight and whether bearings are changing, lights expected next, weather and barometer trend, sail plan and trim, defects or concerns, the skipper's standing orders, and scheduled events (course change, reef). The incoming watch repeats back the critical points.

1. You see a white light over a white light, with a red light below them, fine on your starboard bow. What is it and what should you do?

Answer: A power-driven vessel of 50 m or more, showing her port side. She is crossing from right to left ahead of you or heading away to your left. Take a series of compass bearings. If the bearing is steady and she is getting closer, risk of collision exists. Under power you are the give-way vessel (she is on your starboard side) and must make an early, substantial alteration, normally to starboard and passing astern of her.

1. Why do small alterations of course work poorly at night?

Answer: The other vessel only sees your lights. A small change of heading does not change which sidelights she can see, so she cannot tell you have altered. A large alteration (for example 60 degrees or more) changes the light combination she sees and makes your intentions clear.

1. What is the danger of navigating along the edge of a sector light?

Answer: The boundary is not sharp: there is a transition zone of a degree or two where the colours blend. Steering along the edge, the boat's yaw takes you in and out of the danger sector and you cannot be sure which side you are on. Stay in the middle of the safe sector.

1. When are you on a leading line, and how do you get back on it if the rear light appears to the left of the front light?

Answer: You are on the line when the rear (higher) light is directly above the front (lower) light. If the rear light appears to the left, you are to the left of the line, so move to the right until the lights are in line again.

1. Give four ways to combat fatigue on a night watch.

Answer: Any four of: sleep before the passage and when off watch, keep warm and eat regularly, drink caffeine 20 to 30 minutes before the expected low point, change helm and lookout regularly, keep moving and talking, fresh air on the face, and admitting tiredness so others can step in.

1. How can the echo sounder help navigation at night?

Answer: Set a shallow alarm at a safe depth, corrected for the height of tide. Follow a chosen depth contour. Cross-check soundings with the chart at each fix. Treat unexpected shallowing as a warning to stop and confirm your position.

1. It is 0300, your crew is tired and you are approaching an unfamiliar harbour with a complicated entrance. What options should you consider?

Answer: Wait for daylight: heave-to or stand off at sea, anchor or pick up a mooring outside, or divert to an easier harbour that can be entered safely at night. Entering only makes sense if the approach is well lit, has been fully planned, and the crew are alert enough to execute the plan.

1. A light has a nominal range of 20 M and a height of 36 m. Your eye is 4 m above the sea and the visibility is 10 M. At what distance is it first sighted?

Answer: Geographic range = 2.03 x (6 + 2) = 16.2 M, which is less than the nominal range of 20 M. In 10 M visibility it is first seen at about 16 M (the geographic limit).

1. What is the difference between nominal range and luminous range?

Answer: Nominal range is the range in a meteorological visibility of 10 M, printed on the chart. Luminous range is the range at the actual visibility on the night, which may be shorter or longer.