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The Moiré Effect Lights That Guide Ships Home

submitted by Mordhaus

6 years 9 months 3 weeks ago

I'd never heard of moiré effect beacons until I got an email asking me about them. It seemed like a really clever idea - but it was really hard to research. Or at least it was, until I stumbled upon one magic phrase that revealed its history.

It turns out this thing's called an "Inogon leading mark" or "Inogon light" -- Inogon, not Inogen -- and it's a Swedish invention from the 1980s. But there's still a question: why is being used to mark an undersea cable, instead of guiding people home?

(Full disclosure: there were some weird strobing effects from the light that only showed up when I got the footage into the edit, so the image you see here has been digitally stabilised so it appears the same way on screen as it does in person!)

1 Comment

From YouTube:

Martin Jeffries
2 days ago
Hi Tom, I'm a merchant navy officer who used to work around there, although I never came across this particular light... Sector Lights and Leading lights (parallax) are the internationally recognised marine signals for this sort of use (white light centre, with red and green lights either side to guide you to a safe channel, which i'm sure you've researched and are aware of), but one thing that doesn't come up too often is lines to specifically avoid, and as such there isn't an internationally recognised means of transmitting this with lights. The signal is pointing towards the danger, which is unusual in maritime practice, but it's certainly not a common light and isn't in the IALA buoyage system used for identifying marine hazards.

If it's in a marina, which i think you mentioned, it'll be specifically to stop boats dropping anchor on the submerged cable within the marina's jurisdiction, and it'll be specifically referenced in the marina's or the solent by-laws as an anomalous regulation. (I don't have time to go and hunt it down, but it'll be there as a local reg.) As far as i'm aware, that's the only possible reason for it. It's an unusual solution to an unusual problem. I could of course be wrong...i bring no hard evidence to the table!
Hope it helps

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