Brightness of nav lights and distance visible

[sarabande]

When I started learning Colregs in the end of the 60s, great emphasis was placed by the instructors at Sir John Cass on the correct use of the right kind of oil from the right kind of whale to produce the right amount of light to shine through, yes, the right kind of glass.

A discussion has arisen with a valued colleague about using much bright(er) LEDs to make a boat more visible than the regulation 2 or 3 miles.

Discounting the fact that most boats have masthead lights which at, say, 40 ft ASL will give a theoretical 7.something miles, what advantages or otherwise will accrue from making use of the new Cree LEDS in various multiple configurations to produce a really bright nav light (of the correct colour, of course).

In theory, enough heat could be generated to vaporise any water particles in the immediate vicinity of the lens, , but glare at night from bright lights is destructive of night vision (yes there's whole new thread about the best colour light to enable you to keep night -vision).

With LEDs making batteries 'last' longer, what advantages are there to having really bright nav lights ? For me, height above sea level is more significant, but even that can be counter-productive.



ColRegs Annex 1 is a good start point, talking about minimum visible distance and lots of interesting stuff about spectral frequency.

 

[awol]

...., what advantages are there to having really bright nav lights ?

The hope that the Pride of Bilbao might see you before starting its turn.

 

[lw395]

The eye's response to brightness is logarithmic, so having a light 10x brighter won't be that impressive.
The most important thing is the right colour over the right angles.
If you can be seen 3 miles away and your heading is clear to the other vessel, I think the job is largely done?

Your own lights glinting on metalwork is one of my pet hates sailing on other people's boats.
In mist or drizzle, over-bright navlights could stop you seeing anything else.

 

[Kelpie]

I've been pondering this myself recently. My boat has no nav lights so fitting some is a matter of some urgency (then again, most of my sailing is around midsummer so I have managed to get away with it these last two years).
I was about to click and buy this: http://hmsmarinesupplies.com/epages/950002851.sf/en_GB/?ObjectPath=/Shops/950002851/Products/HMS808 to stick on the pulpit, when I noticed how laughably small it appears to be. Yet the claimed output (lumens) is better than some larger lights. Still, I think it might look a bit silly. But then it won't catch the spinnaker sheets...

 

[grumpy_o_g]

Every so often I'm around when the Barfleur (Poole-Cherbourg ferry) comes in to Poole. You can make out her port nav light against the myriad deck lights from miles out yet they're not at all bright as she goes past you a few feet away. I'd love to know what the trick is.

 

[William_H]

Every so often I'm around when the Barfleur (Poole-Cherbourg ferry) comes in to Poole. You can make out her port nav light against the myriad deck lights from miles out yet they're not at all bright as she goes past you a few feet away. I'd love to know what the trick is.

You will probably find that the nav lights have fresnel lens such that light is directed horizontally towards the horizon and you near but almost under the light will get much less light. One of my little joys in night sailing is to pass close (within 2 metres) of channel marks (we call them spit posts). The light from the red or green lights is dramatically shed on the sail as a bright band less than 1 metre wide and of course parallel to the water surface.
Regarding OP question one would think that brighter is better for being seen. LED certainly do that compared to your oil lamps. So if you fancy a bidirectional on your pulpit then it will be very good. I much prefer the individual LED nav lights mounted on the side of the cabin (watch out for shading from jib) so all wiring is conveniently inside the cabin and the light itself is well away from collision damage. (what you never bump into things or boats?)
good luck olewill

 

[Seajet]

There is the point that at close quarters, say a yacht in a marina, no-one will be looking up at a tricolour on the masthead, so pulpit lights bow and stern are still a good idea.

As for the masthead job, I'd vote for the brightest LED one can get, even if the colours are tinged; with the speed ships and cat' ferries travel at, the important thing is to be seen at all.

 

[Gwylan]

An aspect of all this is that the other party does have to be looking. This is not always the case.

 

[Seajet]

Well that's the point of showing a light or radar reflector isn't it, it's passive.

An active move would be to shine a bloody great searchlight at ships - known in the old days as a ' steamer scarer ' - call them on VHF ( if there's a clue how to, and AIS seems the winner here ) or set off a white flare - even in daytime they're pretty attraction-getting with a lot of smoke too - the snag with that one is it might easily be confused with a distress flare with all sorts of complications & embuggerance for all concerned.

 

[Woodlouse]

I would have thought that a brighter light is more readily seen regardless of the theoretical distance. A masthead tricolour might have a horizon of seven or so miles, but the horizon of the bridge of a large ship could be double that so you might potentially be seen when twenty miles away.

Regardless of that though I think everyone would rather have bright nav lights than dim ones even if it's just for peace of mind and if the brighter lights use less power then that is just yet more reason to go for them.

 

[GHA]

ColRegs Annex 1 is a good start point, talking about minimum visible distance and lots of interesting stuff about spectral frequency.

For anyone interested in building their own, these cree ones were just inside the colour specs, well from memory red was inside and the equivalent green on the edge or the other way round, feel free to do the calcs yourselves..

https://uk.rs-online.com/web/p/visible-leds/8106667/

[FONT=Arial, Helvetica, sans-serif]7. Colour specification of lights[/FONT]

[FONT=Arial, Helvetica, sans-serif]The chromaticity of all navigation lights shall conform to the following standards, which lie within the boundaries of the area of the diagram specified for each colour by the International Commission on Illumination (CIE).[/FONT]

[FONT=Arial, Helvetica, sans-serif]The boundaries of the area for each colour are given by indicating the corner co-ordinates, which are as follow:[/FONT]

[FONT=Arial, Helvetica, sans-serif](i) White [/FONT]
[FONT=Arial, Helvetica, sans-serif]x 0.525 0.525 0/.452 0.310 0.310 0.443[/FONT]
[FONT=Arial, Helvetica, sans-serif]y 0.382 0.440 0.440 0.348 0.283 0.382[/FONT]
[FONT=Arial, Helvetica, sans-serif](ii) Green [/FONT]
[FONT=Arial, Helvetica, sans-serif]x 0.028 0.009 0.300 0.203 [/FONT]
[FONT=Arial, Helvetica, sans-serif]y 0.385 0.723 0.511 0.356 [/FONT]
[FONT=Arial, Helvetica, sans-serif](iii) Red [/FONT]
[FONT=Arial, Helvetica, sans-serif]x 0.680 0.660 0.735 0.721 [/FONT]
[FONT=Arial, Helvetica, sans-serif]y 0320 0.320 0.265 0.259 [/FONT]
[FONT=Arial, Helvetica, sans-serif](iv) Yellow [/FONT]
[FONT=Arial, Helvetica, sans-serif]x 0.612 0.618 0.575 0.575 [/FONT]
[FONT=Arial, Helvetica, sans-serif]y 0.382 0.382 0.425 0.406 [/FONT]


Plus a simple but very good LED constant current driver. (might need a bigger transistor).
https://www.youtube.com/watch?v=Opm-3-hkDEM

 

[lw395]

There is the point that at close quarters, say a yacht in a marina, no-one will be looking up at a tricolour on the masthead, so pulpit lights bow and stern are still a good idea.

As for the masthead job, I'd vote for the brightest LED one can get, even if the colours are tinged; with the speed ships and cat' ferries travel at, the important thing is to be seen at all.

Depends on the circumstances.
The OOW of a mid-size ship has his eye level closer to the level of the masthead than the deck for most of the boats I get to sail.
Inshore, smaller boats will see the lower lights better.

I like to be clear about what my lights are telling other boats. Yachts rarely track a perfect course, even with the electric helmsman, so there's no point worrying about a couple of degrees of overlap, but blurring beyond that is asking for confusion. Knowing there is another vessel there is part one, part two is reading his aspect and responding correctly.

 

[Graham_Wright]

I've often wondered about the trade-off between brightness and area.

Anyone care to shed some light on that?

 

[lw395]

I've often wondered about the trade-off between brightness and area.

Anyone car to shed some light on that?

What's the smallest angle your eyes can resolve?
Can you read text smaller than 2mm at 1metre range, given perfect focus?
So maybe we can resolve an angle of some fraction of a mm in a metre.
So at a kilometre, anything under say 10cm is just a point.
At night, most people have imperfect focus. I have one of those little monocular things, which enlarges by 5 and more usefully, allows fine tuning the focus.

 

[sarabande]

serious practical points being raised, thanks.

One topic I'd like to explore is the use of fresnel lenses (or pseudo-fresnel lenses) in yacht nav lights. The case can be made that directed and concentrated light is fine for steamships and mobos as they tend to be relatively stable, so light is sent out roughly parallel to the earth's surface.

We poor unstable yotties, however, do spend a lot of time tilted over, so nav lights, and especially those with fresnl-type lenses, point either upwards to the stars, or down to the mermaids, and thus reduce the visible output to less than the statutory 2 miles . Neither of which is going to make a good optical impression on the dozing OOW of a Latvian freighter.

Seems to me that, particularly with deck-level nav lights, a levelling device needs to be built into nav lights. A simple damped pendulum to flatten out the effects of pitch and roll, perhaps ? Heath Robinson devotees would no doubt like a gyroscopically-controlled version... Given the small mass of modern LEDs a self-levelling, power-free platform should be easy to make

I'm seriously concerned about the loss of light output from tilted nav lights; every lumen that can fight its way, past reflecting stainless tubing or the total internal reflection of water droplets in mist, towards the optic nerves of lookouts on other vessels increases the chance of avoiding action.

 

[ex-Gladys]

The hope that the Pride of Bilbao might see you before starting its turn.

...only if the member of the bridge team had an up to date eyesight exam as well IIRC

 

[Graham_Wright]

For anyone interested in building their own, these cree ones were just inside the colour specs, well from memory red was inside and the equivalent green on the edge or the other way round, feel free to do the calcs yourselves..

https://uk.rs-online.com/web/p/visible-leds/8106667/

Their angle of emission is stated as 15° so presumably, an array would be needed. If this were mounted on a curved panel at the back of a cylindrical housing, the cut off could be determined by the interference of the housing. Thus the one (or more) towards the forward end would shine aft and those at the aft end, forwards. "Brightness" (however that is defined) could be a variable depending upon how many leds are installed in vertical columns.

……and, if you wanted to go silly, an inboard sensor could choose between high horizontal rows or low horizontal rows according to the roll angle of the ship thus reducing unnecessary dazzle (and current).

 

[William_H]

serious practical points being raised, thanks.

One topic I'd like to explore is the use of fresnel lenses (or pseudo-fresnel lenses) in yacht nav lights. The case can be made that directed and concentrated light is fine for steamships and mobos as they tend to be relatively stable, so light is sent out roughly parallel to the earth's surface.

We poor unstable yotties, however, do spend a lot of time tilted over, so nav lights, and especially those with fresnl-type lenses, point either upwards to the stars, or down to the mermaids, and thus reduce the visible output to less than the statutory 2 miles . Neither of which is going to make a good optical impression on the dozing OOW of a Latvian freighter.

Seems to me that, particularly with deck-level nav lights, a levelling device needs to be built into nav lights. A simple damped pendulum to flatten out the effects of pitch and roll, perhaps ? Heath Robinson devotees would no doubt like a gyroscopically-controlled version... Given the small mass of modern LEDs a self-levelling, power-free platform should be easy to make

I'm seriously concerned about the loss of light output from tilted nav lights; every lumen that can fight its way, past reflecting stainless tubing or the total internal reflection of water droplets in mist, towards the optic nerves of lookouts on other vessels increases the chance of avoiding action.

I think rather than try to fit a self levelling pendulum device or a switching device to detect roll of the boat I would go for more LED facing "to the stars and the mermaids" Consider that the LED in the link has a15 degree wide emission then the LED facing outwards (abeam) would be horizontal with one above it mounted at 22.5 degrees above horizontal to give a beam for up to 22.5 degrees of roll. One below mounted at a similar angle would shine downwards the same amount.
Now the next 3 LEDs facing forward by 22.5 degrees would also have one horizontal and one facing up one facing down.
However the next LED now facing 37.5 degrees forward could be in fact substituted by 2 LED one facing 7.5 degrees up and one 6.5 degrees down. The next LED would face. Finally the next LED faces 52.5 degrees from abeam will not be significantly affected by roll likewise the next one facing 82.5 degrees from beam or nearly forward.
So with 15 degree LED if my geometry is right needs 5 extra LED to make a total 10 LED to cater for 22.5 degrees of roll.
Now not all LED are quite so tightly focussed 30 degree wide being much more common so even easier to cater for roll.
Incidentally I note that the LED in the link does not quote current or power a vital statistic needed in setting up a current regulator. For those running on a simple battery not charged at night a resistor current limiter would do nicely. I found that these kind of LED nav lights really good. https://www.whitworths.com.au/main_itemdetail.asp?item=53179&search123=53179&intAbsolutePage=1
good luck olewill

 

[GHA]

Incidentally I note that the LED in the link does not quote current or power a vital statistic needed in setting up a current regulator. For those running on a simple battery not charged at night a resistor current limiter would do nicely

30mA max , it's all on the data sheet. I made an anchor light from 15 white ones in 5 parallel strings of 3 leds in series each, set to 100mA so each one using 20mA. Should last for decades. The constant current driver is only 3 components and does a much better job at looking after the LEDs than just a series resister.
Also, with the 15deg beam you should see banding from the anchor light, but this dissappears if more than about 20 feet away so all the worry about cut off angles might be better addressed by building one and looking at the real world. Those leds are bright!
And also available with 30deg viewing angles.