Is there a water depth where you are "safe" from dreaded Pot Buoys?

[KAM]

Always wondered about pot bouys in narrow shipping channels. Right in the middle of the sound of Kerrera for instance. Ferries presumably run straight over them at night. Do they get chopped up or just pushed out of the way.

 

[Blue Sunray]

Being that Raymarine mark everything up, are there better hunting equivalents out there? Its resolution is 640 x 480. It reckons 130 yards of vision, so about 120 meters. Its IP67 and has no zoom.

This hunting guy is a third of the price at £150: ESSLNB Night Vision Monocular Scope 5X40 Night Vision: Amazon.co.uk: Camera & Photo . It reckons 200 meters of useful range, has a 5x zoom and has the same resolution of 640 x 480. It's not waterproof

You won't find resolutions much higher that that for Civilian TI due to ITAR.

Thermal Camera Export Restrictions | Infrared Cameras Inc.

 

[AntarcticPilot]

He was the Vice Commodore of bacon butties too ... until we ran out of gas off the North Kent coast... the word mutiny was bandied about...

Edit:
Back from thread drift - one of these is quite expensive at 399 boat credits: Raymarine FLIR Ocean Scout TK 20 degree Field of View - 432-0012-22-00S

Being that Raymarine mark everything up, are there better hunting equivalents out there? Its resolution is 640 x 480. It reckons 130 yards of vision, so about 120 meters. Its IP67 and has no zoom.

This hunting guy is a third of the price at £150: ESSLNB Night Vision Monocular Scope 5X40 Night Vision: Amazon.co.uk: Camera & Photo . It reckons 200 meters of useful range, has a 5x zoom and has the same resolution of 640 x 480. It's not waterproof

Buy cheap... you buy twice?

All that said, let's consider how useful this is in a "watch" situation. If we consider our passage making speed is 5 knots, we'll cover roughly 150 meters every minute, if we assume the most flattering range above of 200 meters, that means the shift orficer would need to check the camera every single minute. If we use the (probably more realistic) range of the Raymarine, that comes down to 0.8 minutes. It would also have the effect of ruining night vision by squinting at a little bright screen every sixty seconds...

Seems not very appealing....

You won't find resolutions much higher that that for Civilian TI due to ITAR.

Thermal Camera Export Restrictions | Infrared Cameras Inc.

I doubt that an IR scope would help very much; they detect differences in temperature, and a pot buoy floating in the sea is going to be at the same temperature as the sea. So there won't be much, if any, contrast between the sea and the buoy. As they also have limited resolution, which can't be improved on much because of the physics of the system (longer wavelength = lower resolution), I suspect that they're in chocolate teapot territory as a means of avoiding pot buoys. The same goes for radar, with even longer wavelengths - a pot buoy is going to be too small to give a good reflection, even if equipped with some sort of reflector.

At night, I don't think there's any reliable means of detecting the usual kind of pot buoy. As Fisherman says, we have to rely on the line being pretty much vertical in the water, so that a boat encountering on simply pushes it out of the way without there being much chance of entanglement. Unfortunately, in shallower water, this becomes less reliable, as the tidal range may exceed the water depth, leaving a lot of slack line at low water. So, this suggests that at night we are safer sticking to water with depths several times the tidal range, even if that means going a long way round. Unfortunately, this doesn't always work - the one and only time I've got entangled with a pot line was in water that was at least 20m deep; perhaps more.

The most visible markers I've seen were marked with Dan buoys, with a flag well above sea-level. There were visible even in limited light, as they showed up against the sky-glow. The usual orange ball is simply not visible at night, unless marked with fluorescent paint.