how to combat dew when using camera gear for long exposures near dewy environments?

[elementgs]

Just a thought.... how about "Neverwet"?

I was watching a video on it tonight and it looks amazing. Water won't even form on the face... not much will actually... the reviews of the product on Amazon claim it's worthless because it wears off too quickly but in this case, nothing but air and water will be touching the lens... right?

My only concern is whether or not it affects the optics itself... I haven't tried it personally. Just curious. Looks almost completely transparent?

Neverwet: Amazon.com: NEW Neverwet Never Wet 2 Part Spray Rust-Oleum 18oz: Home Improvement

 

[elementgs]

Hah. I knew I wasn't alone in this thought. Here you go, solution in hand.The Tokina Rain Dispersion Filter Has No Problem Keeping Water off Your Lens

 

[TCampbell]

A rain jacket wont help.

The problem is, as temps drop, the lens will start to cool. As that happens, dew will condense on it the same as it will on a glass with a cold drink inside (it need not be "raining" -- there just needs to be moisture in the air.

This is my dew controller: DewBuster
These are my dew straps: Dew-Not by AFAB™

That's how I keep dew from forming on my telescopes. It runs off a 12v battery (which is usually really more like 13.8v). The dew straps needs to be the correct size and these are wrapped around the lens just at the front.

I haven't done this for my camera, but this is a case where I probably WOULD throw on one of those UV filters we always tell everyone are worthless. That's because the filter is very thin glass so it doesn't have a lot of thermal mass (unlike the objective element on your lens). This means it'll trap some air between the objective element and the filter making it much easier for the dew heater to keep that space warm (rather than allowing the heat to escape to the night). If you also use a lens hood, it'll help keep the wind & air currents off the glass so it wont lose heat as fast.

 

[Garbz]

Tim shared the way to do it properly but you can do it quite simply as well.

Here's a picture of a setup I've used on a freezing cold night with over 90% humidity.

Those things around the camera and front of the telescope are the dewstraps and are just wrapped around the front element. The sky's the limit when spending, but you can do it very simply too. We use small dew straps for guidescopes which are perfectly suited for an 60-77mm lenses. They aren't all mega straps that go around 8" optics. You can get controllers which monitor the temperature and humidity and provide just the right amount of power to the dewstraps.

However, while we were out there were a few people with very portable and incredibly simple systems which worked perfectly. One guy used a simple dew strap designed for a guidescope hooked to a small 12V lead acid battery. Happily hummed away all night and the day after the battery went on charge. Generating tube currents as Tim mentioned would need to be incredibly extreme on a small camera lens. It becomes critical to maintain control as the focal length increases (especially above 1m) and as the distances between the optics increases (like in a long reflector). If you're generating tube currents in a typical camera lens then I'd be more worried about the melting the lens

/Edit: the controller is visible too, strapped to the left leg of the tripod.

 

[munecito]

Maybe not the solution but when riding the motorcycle in cold weather or rain I use something called "catcrap" (no joke, google it) maybe you can use it on your filter. Mileage may vary nut on the helmet visor and sunglasses it works.

Amazon.com: Ek 123625 Cat Crap Anti-Fog: Sports & Outdoors