Viewing angle of Tri-Colour from dead ahead.

[Adrian Jones]

I'm interested in other owners understanding of the angle that two colours Red/Green are both visible when viewing a boat from dead ahead. Particularly when the boat in question is using a bi or tri-colour navigation light fixture.

I had a conversation with a chap today who claimed he thought both colours were visible over a wider arc, he suggested up to 20 degrees when using a three colour properly aligned LED lamp. He further suggested that when a incandescent lamp is used both colours are only visible over 1 or 2 degrees. This sounded very odd and doesn't make sense to me. It's the red and green filter areas that will dictate the angle over which the coloured lights are visible, irrespective of the light source. Taking a pragmatic view, I can't imagine in practice that any sailing boat would remain steady enough to judge the transition between the two colours anyway.

Any view's? (excuse the pun)

 

[Martin_J]

It is a very precise transition with a normal filament bulb since the correct bulb will have a fine, perfectly vertical single filament.

Too be honest, in the cheaper led units I've not come across one that even comes close to this immediate transition...

 

[Martin_J]

What I tried to say was that if the light source is wider than a fine vertical line that I would expect it to bleed colour during the change at the lens.

 

[William_H]

MartinJ is right. It is the very fine point of light of a vertical fillament that enables the fine definition of red and green from ahead. Putting a white led bulb into this fitting can be hopeless because the LED has a wall of led emitters perhaps 2 cms wide compared to the fillament of less than 1 mm wide. The only way is to fit a bulb with red and green (and white) emitters which can then differenciate to a greater degree before the light hits the coloured lens. Best however is the led emitters without lens. good luck olewill

 

[Wooden Boat Fittings]

Or maybe have a combined light fitting with an internal 'wall' or baffle to cut off the light each side at the right angle -- rather like an internal lightboard. (I can't say I've ever seen one, but it would be the obvious thing I would have thought.)

In any case, each light (port and starboard) should be visible from 0° to 112½° -- ie from dead ahead to two points abaft the beam.

Mike

 

[lw395]

With a conventional, filament tricolour, you can usually see both read and green over a significant angle, when close to it.
At a distance, the light will appear as a point source, the eye will be unable to resolve separate red and green illuminated areas.
Close to it you can see it has a finite size, and the light which comes from its surface tangentially is intense enough to be seen.

With an LED light, the tangential components of the light might well be a bit stronger, but it will still look like a point source from far away.

The ability to resolve both colours instead of a point source will be given at best by the Rayleigh criterion lambda over d, where lambda is wavelength and d is the diameter of your pupil, this gives an angular resolution limit in radians. However most people will not have perfect focus so will see it as one light source from relatively near.

White LED bulbs in conventional fittings are piss poor. End of.

 

[VicS]

Or maybe have a combined light fitting with an internal 'wall' or baffle to cut off the light each side at the right angle -- rather like an internal lightboard. (I can't say I've ever seen one, but it would be the obvious thing I would have thought.)

Mike

I was thinking along the same lines, but it may not be an easy modification to an existing lantern.

I have an Aquasignal tricolour to which I have fitted a three colour LED unit like this

I accept that the cutoff between the colours may not as sharp as with the original filament bulb but I hope it is better than it would be with a non sectored warm white LED fitted.

 

[cryan]

It shouldn't matter what the light source is as the fitting should have a solid partition which stops light transmitting through it which should give a crisp and definite transition.

 

[jwilson]

It shouldn't matter what the light source is as the fitting should have a solid partition which stops light transmitting through it which should give a crisp and definite transition.

To get a solid transition on a bicolour or tricolour you need a long enough partition, which just doesn't fit in a normal modern lamp housing - look at the lightboards seized to the shrouds on a traditional boat - http://www.yachtsnet.co.uk/lightboard.jpg - that one is over three feet long. The sidelight to stern light transition is less critical, what matters on a sailing yacht is the red/green cutoffs, which has to be reasonably good (perfection is near impossible without huge "partitions" or complex optics). When altering course to avoid someone at night we don't make tiny course adjustments, they should be definite.

I've just changed steaming light and stern light to LED, but have left a filament bulb in the bicolour. I tried an LED in the bicolour, and just walking round an adjacent pontoon it was clearly inferior.

 

[lw395]

It shouldn't matter what the light source is as the fitting should have a solid partition which stops light transmitting through it which should give a crisp and definite transition.

The solid partition only works if the light source is very close to it, which means the light source needs to be concentrated very close to the centre of the fitting.

How good is good enough though?
Most yachts change course by say 5 degrees all the time, so perhaps that's a realistic target?
In some ways the green/white divide is the critical one, you will probably see the boat dead ahead, but the one coming in on the quarter seeing your green may catch you out?

 

[Carioca]

I was thinking along the same lines, but it may not be an easy modification to an existing lantern.

I have an Aquasignal tricolour to which I have fitted a three colour LED unit like this

I accept that the cutoff between the colours may not as sharp as with the original filament bulb but I hope it is better than it would be with a non sectored warm white LED fitted.

Take care with these, I inherited an Aquasignal tricolour fitted with one of these lamps, when testing it on the bench it looked very strange, closer examination showed that the lamp was not correctly registered with respect to the lens filters. With LEDS which have a very closely defined colour putting a green led behind a red filter means not a lot of light and vice versa. With the registration adjusted it looks acceptable though because LEDS are very directional I do wonder just how visible LED lights will be on a pitching and rolling boat.

 

[Oldhairy]

I'm interested in other owners understanding of the angle that two colours Red/Green are both visible when viewing a boat from dead ahead. Particularly when the boat in question is using a bi or tri-colour navigation light fixture.

I had a conversation with a chap today who claimed he thought both colours were visible over a wider arc, he suggested up to 20 degrees when using a three colour properly aligned LED lamp. He further suggested that when a incandescent lamp is used both colours are only visible over 1 or 2 degrees. This sounded very odd and doesn't make sense to me.
)

The chap you spoke to had it right. I had expected a reply to your question before now.
COLREGS ANNEX I / 9(a) (i) In the forward direction............practical cut off between 1 degree and 3 degrees.........
(ii) ...........at 22.5 degrees abaft the beam.....decrease steadily to reach practical cut off at no more than 5 degrees outside the prescribed sectors

 

[KellysEye]

>Particularly when the boat in question is using a bi or tri-colour navigation light fixture.

COLREGS require a tricolour.

>he suggested up to 20 degrees when using a three colour properly aligned LED lamp.

Each colour shows for 120 degrees. I don't know if it has changed but LED white lights looked blue.

 

[Adrian Jones]

The chap you spoke to had it right. I had expected a reply to your question before now.
COLREGS ANNEX I / 9(a) (i) In the forward direction............practical cut off between 1 degree and 3 degrees.........
(ii) ...........at 22.5 degrees abaft the beam.....decrease steadily to reach practical cut off at no more than 5 degrees outside the prescribed sectors

Surely the red and green filters provide the required cut off angles as defined in the COLREGS. Navigation light manufacturers build and position the filters in their fixtures to ensure that light is emmitted over the correct angles. The fixtures will show red, green and white light over the correct COLREGs prescribed arcs, due to the structure of the light.

 

[pyrojames]

Surely the red and green filters provide the required cut off angles as defined in the COLREGS. Navigation light manufacturers build and position the filters in their fixtures to ensure that light is emmitted over the correct angles. The fixtures will show red, green and white light over the correct COLREGs prescribed arcs, due to the structure of the light.

The cut offs only work properly if the light source only comes form the centre of the prescribed centres. If the light source is off to one side, the sectors will be wrong, if the light source is too large, then the sectors will overlap.

 

[lw395]

The cut offs only work properly if the light source only comes form the centre of the prescribed centres. If the light source is off to one side, the sectors will be wrong, if the light source is too large, then the sectors will overlap.

Exactly.

 

[Oldhairy]

To paraphrase pyrojames , the light will only work properly with the light source that the fitting was designed for, correctly installed.
@Kellyseye. COLREGS do not require tricolour. It MAY be used instead of side and stern light for vessels under 20m (Rule 25a i & ii )

 

[Ian_Edwards]

Practical tests on LED in Series 40 Tricolour

Hi,

These photos are my bench test of a replacement tricolour LED in a series 40 tricolour housing. they were taken at 30 and 15 degrees either side of viewing from dead ahead, plus a view from dead ahead.

I've no idea whether this combination of LED and lens (designed for a vertical filament) would pass muster in terms of collision regulations.

After thinking about it a bit, I sold the LED and Tricolour lamp separately and bought a new purpose built combine Tricolour and Anchor light LED unit.

I'm happy to admit that these are close range shots and that the eye is unlikely to be able to resolve the the difference at a practical range (100's of meters), but I felt that there was to much bleed through of the colours, and didn't want to take the risk of any ambiguity, in what may be a safety critical situation.

 

[VicS]

Take care with these, I inherited an Aquasignal tricolour fitted with one of these lamps, when testing it on the bench it looked very strange, closer examination showed that the lamp was not correctly registered with respect to the lens filters. With LEDS which have a very closely defined colour putting a green led behind a red filter means not a lot of light and vice versa. With the registration adjusted it looks acceptable though because LEDS are very directional I do wonder just how visible LED lights will be on a pitching and rolling boat.

True

When I bought mine it was supplied with a holder, to replace the existing holder, which allowed the LED assembly to be aligned with the filters ( and the boat)

If it had been plugged into the existing holder it would have been a very long way adrift from correct alignment. ( more than 90° IIRC)

Presumably it was a "universal" replacement for a filament bulb, not specifically for the Aquasignal lantern into which I was fitting it.

Interestingly the LED unit was not marked to show which was front etc and the LEDs all look the same. The first job was therefore to power it up and mark the front!

I posted this info together with photos at the time.

 

[blackbeard]

Hi,

These photos are my bench test of a replacement tricolour LED in a series 40 tricolour housing. they were taken at 30 and 15 degrees either side of viewing from dead ahead, plus a view from dead ahead.

I've no idea whether this combination of LED and lens (designed for a vertical filament) would pass muster in terms of collision regulations.

After thinking about it a bit, I sold the LED and Tricolour lamp separately and bought a new purpose built combine Tricolour and Anchor light LED unit.

I'm happy to admit that these are close range shots and that the eye is unlikely to be able to resolve the the difference at a practical range (100's of meters), but I felt that there was to much bleed through of the colours, and didn't want to take the risk of any ambiguity, in what may be a safety critical situation.

Thanks for this, Ian, seems to be worth any amount of theory.
On whether the combination of LED and lens is consistent with COLREGS, the answer AFAICS is a resounding and definite NO.

Incidentally. I suspect that some combination of red and green seen together might possibly give a sort of mucky white. Which might not give the impression we are trying to convey.
Also incidentally; does anyone know what the cut-off angles for a purpose built tricolour LED (ie no lens) are? I must admit I can't see how it might be compatible with COLREGS but I am prepared to be convinced if someone can show actual measurements/illustrations to the contrary. Failing which, I will stick with a filament bulb.