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There were a couple of times yesterday where, during an intense bit of rain, our visibility was reduced to almost nil. Of course, both times this occurred we were attempting to travel under bridges, one of which was a swing bridge. We knew they were there and had even made contact with the swing bridge tender but we were almost on top of the bridge before we could make it out.

It may sound obvious but visibility plays a huge role while navigating, which is no doubt why binoculars are such an important piece of boaters’ kit. The primary navigational aides, lateral buoys and daymarks are colored red and green so that they can be easily distinguished but they are also shaped differently (red “nuns” are pointy and green “cans” are square topped). This is important because, at least for me, before the colors can be determined you can often distinguish the shape of the mark.

I found the following on John Vigor’s Blog:

Boater’s Rules of Thumb, #57

In clear weather you can distinguish the shapes of prominent lighthouses, or houses, and trees from about 8 miles away. Individual windows in a building are discernible at about 2 miles. A person at 1 mile is a moving black dot without limbs. The movement of a person’s legs, or a rower’s arms, is discernible at 400 yards. You can make out a face, but not recognize its owner, at 250 to 300 yards.

The above is good info because it tells us when we have to put our clothes back on when we are doing some sailing Au Naturel. 🙂

All markers come with at least one guard bird. This one must have been special because it had three guardians.

This marker’s guard bird must be out on patrol but you can see his nest.


  1. When the weather’s kind of crappy
    and the crew just ain’t too happy
    and the First mate’s face is frozen in a frown;
    To avoid a boat collision
    It would be a good decision
    To just stay in bed and leave the anchor down.

    (Cap’n Larry)

  2. Love it – your comments on the bird patrol are funny!

  3. I think there’s a fourth bird behind the lamp on that marker! Maybe one of them is the guardian bird for the opposite marker!

  4. The “Boater’s Rules of Thumb, #57” only applies to unaided eyes – binocs can see *much* further, so keep that in mind when when exposed…

  5. Here is the cynical version of me (I’ve been ashore too long!):

    The birds are actually genetically engineered mobile paint removing avians. Their primary purpose is to ensure that the USGC keeps buying paint ;D.

    Fair Winds,

  6. “before the colors can be determined you can often distinguish the shape of the mark” – Especially so when conditions are less than perfect. Our densely packed rod cells (sensitive to light intensity, but not to colour) give much better resolution and low-light capability than the relatively sparse cone cells (good for colour, not so much for low light). Add a bit of fog, or wait until twilight, and we can still see shapes just fine but colour disappears.

    I’m curious if you have any thoughts on night-vision gear, Mike? Either the (expensive) military-surplus intensifiers, or the (obscenely expensive) infrared stuff could be interesting to try. I keep coming across articles about the latest and greatest $30,000 IR cameras for the megayacht crowd; meanwhile, I just come back by sunset when in unfamiliar waters (and occasionally use a couple of spotlights).

    I seem to recall a lockstation near here (Lower Brewers, I think) that lost its guard osprey a couple of years ago. Something about the lightning storm that came by while we were waiting to lock through farther up the canal… poor bird…. yours (cormorants?) look quite happy up there.

    • I haven’t really given any thought to the night vision stuff, nor have I tried them. I have used our binos at night though and find that they do help to gather some light. I’m sure with an unlimited budget I’d want something like that on board.

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