Impaired night vision from masthead light!

Dear All!

I work on a 34m MY which have a serious problem during night passages: the (stray) light from the masthead light is lighting up the whole foredeck and (especially) the white bulwarks which are at perhaps 45 degrees angle.

The result is that night vision is badly affected and the lookout can't really see properly. If (as a test) the masthead light is turned off it is like putting night vision glasses on.

We have tried with a simple shade to block the light but the shade has to be unreasonably big to block all light so this is not a viable solution.

- Has anyone else had this problem? If so what was your solution?
- Would it be possible to alter the actual light? I.e. to put a shade inside the light or perhaps paint the Fresnel pattern of the lens?
- Are there nav lights that have a maximum vertical arc of light close to the 5/7.5 degrees required?

All ideas are welcome since this is a quite serious problem for us.

Thanks for your reply!

Exactly what we expected when we made our first shade! In our case it seems like the light is not focusing properly which means that we have to block light also from the top Fresnel pattern of the lens. (That probably didn't make sense at all!!! I will try to do a drawing with the actual measurements on our yacht and post later...)

Do you have a picture or a drawing of your shade?

Best regards.

Here is a photo of our experimental shade. The length is 320mm from the fwd end of the light. The light is mounted approximately 17m from the bow and 6m above deck. This is more or less the same as the ratio between the length of the shade and the height of the light meaning that we have to obscure the complete light (as seen from deck level).

I thought that the Fresnel lens focused (almost) all light horizontally and that we therefore only should have to block the lower part of the light, i.e. use a shorter shade.

Two notes:
1. The lens is not really clear and should probably be replaced.
2. The pattern on the lens is rather "corrugated" than a proper Fresnel cut.
Can these things increase the dazzling effect?

Best regards!

Yes, I agree with the lens. The light seems to be of the brand "Krachtig" which I can't find on the internet so we probably need to change the whole assembly. (Just a matter of convincing the owner...)

However I don't think that we should tilt the light. That would affect the range and would most likely be illegal. Thanks for helping us to find a solution though!

I don't want to be a "besserwisser" but lenses actually changes the direction of the light rays. The whole purpose of a Fresnel lens is to focus the light in a specific direction.

Please see http://en.wikipedia.org/wiki/Fresnel_lens

Best regards!

Thanks for the tip! Ours are probably too old to be found but the DHR
lights seem to be a good replacement.

Yes, we have decided to try to make a shade but your suggestion to replace
the lens with a clear one will not only improve the range but hopefully also
reduce the dazzle.

Thanks to all who have replied!