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Old 10-04-2019, 01:03 PM   #41
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What we were taught in military aviation is that the average person loses half of their night vision every 10-15 years.


Hopefully Dave our eye Doc can chime in with more recent data.

Iím not aware of an specific statistic Scott. Iím also not sure that it would hold true today. There are several reasons why our night vision is worse as we age.

The first is that our pupils get smaller over the years. At 61 years old, there is a lot less light entering my eye because of a smaller pupil than when I was 20 years old.

Secondly, the cornea and lens of the eye become less clear over time (cataracts anyone?). This causes increased glare. That increased light scatter spreads the bleaching affect of a point light source around the eye. That is one reason we have more trouble with night driving as we age.

Finally our ability to regenerate the photopigments in the eye that actually receive the light decreases over time. Part of this is simply a slowing of metabolism with age. Part of it is decrease blood flow to the retina and decreased O2 saturation. That is why smoking is so detrimental to night vision. With any type of bright light, the rods in the retina are bleached out very rapidly. This means that all of the photopigment is depleted in the photo-receptor. This has to be replaced by the outer layer of the retina and takes a while. The cones do the same thing but their photopigments are replaced much faster as they have two ways two biochemical routes to replace the pigments.

Bottom line is that the rods are our most sensitive low light receptors. Back in the day, the navy would have lookouts posted above deck, away from any light source and the ship would run dark. This allowed the sailors to fully dark adapt and they had incredibly sensitive night vision as a result. Sailors were warned however than even striking a match would mean a half hour of recovery time for the night vision.

We donít operate in scotopic conditions (ie rods only) but we operate in low light which gives us a combination of rods and cones. However, any bright light, even brief, which take out the rods and therefore our low light sensitivity.

If you are ever looking at something at night and cant tell what color it is, you are experiencing mostly scotopic vision, as your cones are inactive with not enough light to stimulate them.

Most of what has been said already I agree with. It takes only a second to ruin your night vision and then can take 30-40 minutes to be fully dark adapted. I avoid using my spotlight. I also have all illumination extremely dim in the PH during night operation. I will use a spotlight when coming into an unfamiliar marina at night if I need to identified a dock or slip number. However, I donít use it while cruising. The problem with the spotlight is it will allow you to see what it illuminates, but will prevent you from seeing anything else. The use of a spotlight makes it all but impossible to see the navigation lights of other boats at a distance. My feeling is, if you donít feel you can safely run at night without lights, you shouldnít be running at night.

As has been mentioned, it also is dangerous for other boaters who have their own vision bleached out by your spotlight.
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Old 10-04-2019, 01:03 PM   #42
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I have a super high power custom-built flashlight that has a very narrow bean with little scatter.
Just out of curiousity, where do you get one of these? Sounds like a useful tool.

I carry a portable plug-in megawatt xenon whizbang spotlight. I may have used it 3-4 times in a decade - in tight marsh channels at night. Generally not worth the sacrifice of night vision. However, when you need it - it's a good thing to have.
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Old 10-04-2019, 01:44 PM   #43
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There are several reasons why our night vision is worse as we age.


Secondly, the cornea and lens of the eye become less clear over time (cataracts anyone?). This causes increased glare. That increased light scatter spreads the bleaching affect of a point light source around the eye. That is one reason we have more trouble with night driving as we age.
Dave, thanks for the cogent explanation.

I will add this: Many of us have gone through the cataract phase, and now with lens replacements, have overcome that deficiency. It is important to note that the other effects of aging eyes are not eliminated by the simple expedient of cataract removal, even though the immediately improved vision, including improvements in night vision, can be quite dramatic.
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Old 10-04-2019, 01:57 PM   #44
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dhays wrote, "My feeling is, if you don’t feel you can safely run at night without lights, you shouldn’t be running at night."

For the reasons that he and Comodave each explained, that's the bottom line. The spotlight is there to positively identify a marker number or an unidentifiable object. Otherwise, it should be left dark.

For for several years I earned a living running the ICW and crossing bays / sounds at night, in an inspected T-boat with a 1M CP spotlight. In all those years I may have switched it on for a cumulative grand total of sixty seconds, dousing it as soon as possible. As for playing a light on another vessel, it's not just rude but dangerous. (Confession: more than a few times that bright spotlight helped wake up a sleeping bridge tender)!
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Old 10-04-2019, 02:09 PM   #45
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Guess all those tugboat and other commercial captains who use their searchlights shouldn't be running at night.
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Old 10-04-2019, 02:42 PM   #46
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We run at night on the ICW and inland rivers. When running from channel marker to marker it is a MUST to use a good high power spot light.

We have CF 12" 24 VDC 1.6 Mil CP spot light that is mounted on top of the pilot house it will reliably show markers at one mile. It has a very narrow beam and is very easy to keep out of the eyes of on coming boats or tugs. With out this it would not be possible to safely run at night in narrow river channels.
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Old 10-04-2019, 02:43 PM   #47
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Read the USCG regs concerning commercial boats and ships transiting at night. It might enlighten you.
Or you could read Chapman's and look at the pictures.
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Old 10-04-2019, 02:57 PM   #48
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We run at night on the ICW and inland rivers. When running from channel marker to marker it is a MUST to use a good high power spot light.
........
how far apart are these markers that you need to see them a mile away? any channel I have entered has the first marker lite, then the following markers are within sight of each other on fog free day or night.

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Read the USCG regs concerning commercial boats and ships transiting at night. It might enlighten you.
Or you could read Chapman's and look at the pictures.
Maybe, but care to quote the part you want us to read?
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Old 10-04-2019, 02:59 PM   #49
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Guess all those tugboat and other commercial captains who use their searchlights shouldn't be running at night.
At least not with their spotlights blazing away and shining into my eyes.
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Old 10-04-2019, 02:59 PM   #50
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We run at night on the ICW and inland rivers. When running from channel marker to marker it is a MUST to use a good high power spot light.
Depending on moonlight and other visibility conditions, not necessarily. A good pair of binoculars can help a little in dim light as well. But this is generally the point where I'll send someone up to the bow as an extra pair of eyes to help point at channel markers in case they see them before I do.
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Old 10-04-2019, 03:15 PM   #51
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OK, down in the weeds now.

Maybe this, maybe that.

Saying you always need to run with a light on is like saying you never need to

I have done both and saw the merit in both.

To only be on be side seems to me maybe there's a boat, or oerations, or stretch of waterway, or single handed, or a visibility issue, or ad infinitum that maybe you just haven't come across.....
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Old 10-04-2019, 03:32 PM   #52
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Would all of the "Captains" on here who have run a tug at night pushing a six barge tow in a twisting narrow river channel and nine feet of water with markers barely visible PLEASE HOLD UP THEIR HANDS!

A barge is 195' X 35'.
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Old 10-04-2019, 03:42 PM   #53
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how far apart are these markers that you need to see them a mile away? any channel I have entered has the first marker lite, then the following markers are within sight of each other on fog free day or night.


Maybe, but care to quote the part you want us to read?
BIG freighters and cruise ships must be 'well lighted' ie white deck lights.
Tugs with tows, the mast lights of the tug will tell you a lot.....
The towed barge must display lights too.
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Old 10-04-2019, 03:46 PM   #54
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Would all of the "Captains" on here who have run a tug at night pushing a six barge tow in a twisting narrow river channel and nine feet of water with markers barely visible PLEASE HOLD UP THEIR HANDS!

A barge is 95' X 35'.
barge is 95' X 35' times 6?
You probably drive an 18 wheeler train in downtown rush hour traffic during the day.
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Old 10-04-2019, 03:47 PM   #55
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BIG freighters and cruise ships must be 'well lighted' ie white deck lights.
Tugs with tows, the mast lights of the tug will tell you a lot.....
The towed barge must display lights too.
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Old 10-04-2019, 05:08 PM   #56
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Count the wheels there are more than 18
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Old 10-04-2019, 05:26 PM   #57
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I rather agree with using the right tool at the right time, in the right way.

But as a reminder as to how dynamic the scenario can be. A few times Iíve caught myself peering into the dark, partly frustrated with the moon, partly with the noise pollution on shore, partly with the tide rips obscuring the next log out to get me, remembering the last one. I realize suddenly that everything is annoying me less, the background shore light is gone and instead of relaxing, Iím suddenly paranoid. Then it hits me. The shore lights did not dim, their missing, except for those white lights over there, and and are they slightly moving?

Gaaah, freighter!!!!

Running up Admiralty, even when out of the traffic lane, your not out by much. Sometimes itís not about what you do see, but what you donít see.

This was before ais, and I had no radar on the fly bridge at the time.

Itís not always easy to recognize when one is truly using all their tools at hand. Easy to miss even big things at night. Like when that little green you saw over here did not seem to be related to that white light way over there! Got to stay alert and on your toes!
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Old 10-04-2019, 05:43 PM   #58
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Having run both the ICW and all over the PNW, I'd a lot rather run the ICW at night than the PNW. In the ICW, everything is pretty well charted and where it is supposed to be, generally the seaway is modest or non-existent. In the PNW, trees large enough to show up on radar are floating about at random, along with the same size logs just barely beneath the surface. Not just occasionally but quite frequent. Add to that a 4 or 5 foot short seaway (20 knots against a 3 knot current) and you might just as well point that spotlight right at your eyes for the good it will do. Preserving your night vision may help to look astern and see what just holed your boat, that's about it.
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Old 10-04-2019, 05:47 PM   #59
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Situational awareness at all time!
Sight and SOUND.

We had a boater upset with a local lake boat rental agency that refused to rent a PWC to him, a person with a hearing loss.
The rental owners reasoning is that you must maintain a lookout by sight and SOUND (USCG Nav Rules) and the renter obviously could not hear.
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Old 10-04-2019, 05:57 PM   #60
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The previous owner of our boat must have been a commercial fisherman. A dual high power movable spot light pointed forward, three one thousand watt halogen flood lights, one to pointed to each side and one astern. Of course, one would need to run the generator for that light show. Might come in handy if we were about to be run down by a freighter.
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