Backwards (mis)use of a GPS - Page 3 - SailNet Community
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post #21 of 25 Old 09-04-2008
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My sextant has a green LED that works very nicely. It illuminates an area only about the size of a thumbprint...perfectly adequately!

Now that LEDs are getting cheaper, I am thinking of installing downward pointing red LEDs to illuminate steps, handhold, ways to the head, etc. It seems a way to show where the important stuff is specifically, while preserving night vision (I can sit in the head, and in the pitch dark, the tap and the towels aren't going to be an issue).

The point is that on a moonless, cloudy night, the "cut-off" between dark-adapted vision and virtually blind can be sudden, and really dim red LEDs could save a twisted ankle or a concussion from missing a handhold.

My aft cabin is like a cave, with only two aft 7 x 14" portlights, and so I had to think creatively.
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post #22 of 25 Old 09-04-2008
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After looking at some of the LED replacement bulbs that are available now, I'm seriously considering relighting my entire boat. I actually need my guages a little brighter but I would like to tone down the cockpit lighting a bit.

Anyone know how bright (in lumens) a light has to be in order to be visible at 2 miles?
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post #23 of 25 Old 09-04-2008
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Not an easy answer, as it is the lamp and not the bulb (LED) that has to be visible at 2 nm. The vertical filament bulb has the advantage of a sharp sector cut-off when correctly placed in the lamp. The LED lamp needs to be specially designed to meet the cut-off requirements, and have fairly uniform brightness across the required angle in azimuth and elevation.

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post #24 of 25 Old 09-04-2008
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[QUOTE=halekai36;363044]Having tried them many times I can assure you they will destroy your night vision! I still have one on board for emergencies but not for general steaming. If you do use one you really need to get it out over the bow pulpit to avoid any deck reflections. Even then the glare off the water will still kill your night eyes.

We sail regularly into the Port of LA at night and the glare off of the commercial docks, cranes and massive container ships are absolutely blinding. I ALWAYS have a lookout at the bow with a portable light and even then it is iffy on really dark nights. Leaving port on the other hand is pretty cool, we can make hand puppets against the backdrop of Catalina Island and we can show home movies on the sails by just holding up the camera
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post #25 of 25 Old 09-04-2008
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How about this. Hang a wrist watch with a glow in the dark face in the cockpit.
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