The Offshore Voyaging Reference Site

Can We Really Be Seen By Ships at Night?

Some days ago we made an overnight passage from Nova Scotia to Newfoundland. At about 2:00 am, Phyllis picked up a slow-moving target at about 2.5 miles on radar.

Despite it being a dark and clear night, with a tiny sliver of waning moon low in the sky, we could see no lights, even through our high-quality Steiner binoculars, and they suck light.

Finally, when the target was just 1.5 miles on the beam, and against the blackness of the land, we were able to just barely discern a very faint white glow that we finally recognized as a steaming light reflecting off the target’s headsail—indicating a sailboat motorsailing—but during the whole encounter we never saw red or green sidelights, and we only saw said glow because the radar was giving us the exact bearing to direct the Steiners on.

I gave them a call on VHF and was immediately answered with the information that they were indeed a sailboat motorsailing.

And then, when the range had closed to about a mile, an AIS target came up on our plotter for the very first time. Said target only showed the other boat’s name for a moment or two and then reverted to an MMSI number before blinking out completely at about 1.5 miles.

I took two important lessons away from this encounter:


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Ernest

Hi John, for sure an interesting and vital topic. And of course AIS visibility of a vessel always depends on the AIS being switched on at all … in the Med, for example, trawlers who are either actively fishing or moving to their hunting grounds tend to deactivate AIS as to not give their location away to other fishing boats. And in Greece I once had a Superfast ferry (one of these really fast and huge ferry boats running at 25+ m/h) having the AIS switched off as it took a shortcut that is forbidden for commercial traffic.
AIS can also be an issue esp. in Croatia when you are not navigating exactly or don’t take the country border line into account – crossing the border line with your AIS active might present you with a nice surprise when back in port where the harbour police will fine you for crossing the border without clearing out first. They charge up to 2k EUR per peron for this. So a lot of recreational boaters turn off their AIS when navigating near the border.

Ernest

Actually there is a remote rocky island called Palagruza which belongs to Croatia, thus extending the 12mi border. The topology of this island creates a “dent” in this (imaginary) line, so navigating correctly is a bit tricky, some boaters simply take the straight line and thus leave and reenter the croatian waters, albeit only for approx. 2nm. Which makes for some nice extra income for the tax office.

https://joergredl.files.wordpress.com/2008/05/segeln-georg-2-127.jpg

Enno

Interestingly short sighted behavior for officials.
They are not only compromising security at sea because they effectively encourage people to switch off their AIS, they are also compromising their own growing yachting industry by discouraging people to visit.

Francisco Moreno

That the Croatian authorities specialize in tracking boats via AIS and then fining them for any number of reasons based on their AIS track is a well-known fact.

They are even said to come to your boat with a printed track of your boat when they approach to charge the fines!

Marc Dacey

There’s other reasons to switch off AIS transceivers and even lights as well. Going through the Sunda/Malacca/Singapore Straits is going through pirate waters, although most of this is directed to commercial vessels. An added issue are unlit fishing boats which may be easier to avoid from a deck made as dark as possible. The Red Sea has quieted down of late, but more than once I read of sailing yacht “convoys” going dark, transceivers off and radio traffic very limited to pre-arranged channels so as to make their detection by pirates as difficult as possible.

While this is not the case described by John, the result is the same: don’t count on the traffic you meet at sea being lit up in several frequencies. There are reasons beyond “bad coax” why they may not be. Interestingly, however, despite the fact our boat is exactly one cm. short of 12 metres LOD for now-obscure tax purposes, I have always upsized the lights to the greater than 12 metre standard. When I want to be seen, I want no ambiguity about it. Tiny 10 watt lights (as are legal below 12 metres LOD in Canada) at night are very hard to make out on smaller boats.

David

When we last had our mast down for re-rigging, I went ahead and installed an led tricolor light at the masthead. The thought was that the added height would be beneficial in rough seas when the conventional sidelights might be obscured by wave action, but after reading this, I’m inclined to use the tricolor more regularly when offshore. I am aware that one cannot legally use both sets of light simultaneously. We do not have radar and only have an AIS receiver and while we do appreciate the data sets it produces, for our situation, an alert pair of eyes is still our best line of defense.

Peter Mahaffey

Well that article hasn’t exactly done a lot for my confidence in the McMurdo S20 personal AIS beacon which I wear at night when on watch during offshore passages. Its supposed to have a range of 5-7 miles at sea level, with its fragile little antenna. Now we hear that even on a 14 m yacht with antenna mounted several metres above sea level, the range might only be a mile of two.

Marc Dacey

That matches with the height of the antenna at the masthead combined with the compartively low wattage. I did some tests a while back using a SH HX850 handheld (six watts on high power) taken out into the lake and used to reach my wife on our boat with a masthead antenna on a pre-arranged channel. Six miles was about the workable limit where I could be heard above the static, under “best conditions”. So I generally cut that in half for “average conditions”. Given that AIS beacons/tags operate on the same frequencies, your numbers make sense. On a fast boat, that doesn’t give a lot of time to react, come about and try to find someone in the dark in the water. That’s why I like those beacons that set off a big alarm if the wearer gets more than 20m (or whatever) away from the VHF. Of course, how many people keep the VHF on 24/7 on passage? Some do not.

Ted

We use our tri-light when motorsailing, as does pretty much every other sailboat we see out here. It may not be legal,but is a lot more visible and therefore safer. Our Vesper watchmate has worked brilliantly for the two years that we have had it. The fishing fleets here in the South Pacific, mostly Chinese or Japanese, do not show AIS and can be a significant hazard

Ernest

To be honest, I’d rather be illegally seen than legally run over.

Ernest

😉
It was mainly for the obvious pun – and as you said, today’s LEDs are quite bright.

Ernest

A “legal” alternative is also the masthead allround red over green in addition to the nav side lights (COLREGS Rule 25.(c)).

Enno

Hi Ernest
In my understanding of the colregs a sailingvessel that is motorsailing is legally a powerdriven vessel which means that rule 23 applies. That means no red over green is allowed. Correct me if I’m wrong.

Ernest

Of course you’re correct – I meant it for sailing vessels. A vessel motoring shows the steaming light which is already well above the side nav lights and _should_ make it visible. Which unfortunately is not always the case given Johns story above…

Paul

This is true, but the white steaming light is the solution here, as it gives the visibility whilst motoring or motor sailing. The issue in the story is not that they didn’t have a steaming light, but most probably where it was mounted. For some reason I can’t understand, sailing yachts now come with the steaming light mounted about 2/3 of the way up the mast. This has been the case as long as I can remember (about 30 years), and I can’t find any reason for it in Colregs. When mounted at this height, and motor sailing, it is sometimes obscured by the sails.

Colregs doesn’t dictate a maximum mount height for the steaming light, only a minimum. Thus it makes absolute sense to mount it at the masthead. This provides greatest distance and minimum disruption by sails when motor sailing.

Unfortunately almost no sailboats come with a masthead steaming light as standard: it’s almost always fitted 2/3 up the mast. So such a light is a retrofit, which almost nobody does.

I have no idea why this is the case.

We refit our boat with Lopolights about 7 years ago. Not withstanding earlier posts about Lopolight reliability, we have had no issues. We have the all round red over green, and our steaming light is part of our masthead anchor light: when anchored it’s an all round, when steaming it’s just the front portion lit. I think it’s the best solution.

Cheers,
Paul.

Matt Marsh

I’m strongly in favour of setting up the boat to follow both Rule 23a and Rule 25c precisely. That is:
– red, green, and white sector lights at deck / cabin level, used all the time
– red over green all-round lights at the masthead, used when sailing
– white masthead light (excluding aft sector), used when motoring

I honestly don’t like masthead tri-lights, by comparison, although they are better than minimal deck-level sector lights. From a distance, either type appears as just a single dot of one colour. The full Rule 25c setup, by comparison, makes it pretty easy to tell that I’m looking at a sailboat, that it’s about yay big, and that it’s about yonder far away.

Skimping out on lights sorta-kinda made sense when batteries were limited, incandescent bulbs were hungry, and the seas were mostly empty. These days, I can think of no reason not to use the full Rule 23a / Rule 25c setup.

Ernest

For a sloop there seems to be no reason to not have the steaming light mounted on the mast top as to Rule 23.a.i ( A power-driven vessel underway shall exhibit: a masthead light forward) – no min/max height specified here. Rule 21.a defines ” “Masthead light” means a white light placed over the fore and aft centreline of the vessel showing an unbroken light over an arc of the horizon of 225 degrees” which basically would make a position that keeps the light partially obscured by sails illegal (“unbroken”).
Any ketch, yawl or schooner might choose to show a second steaming light (even if not obliged to, Rule 23.a.ii) which again must be located higher than the forward one, thus dictating to mount the forward light lower than the mizzen height.
If I had a two master I’d certainly opt for two bright LED steaming lights.

Dave

I have had issues with several AIS transponders. One from heat issues, one from a bad automatic antenna switch and the last from a damaged coax cable installed on a brand new trawler. Imagine traveling through N. Y. harbor and seeing only five AIS targets.

My mother in-law checks the the performance of our transponder using the Marine Traffic network. I find out quite quickly if something is not working properly.

Marc Dacey

I have a father-in-law who was a one-time yacht designer. I think he can be relied upon to perform a similar function. It’s a great way to self-check.