Condensation prevention

[Cloggy]

Does anyone have any tips for preventing condensation when using a camera for a prolonged period during the night?

I started taking a series of startrail pictures and after 15 minutes the lens starting fogging up.

Most frustrating!

 

[Big Andy]

Heat is the obvious answer but how to apply it is the problem. I know some people have used the hand warmer packs you can get at outdoor shops and just place them on the lens hood for long exposures and say it works although I haven't used them myself.
http://www.gooutdoors.co.uk/hi-gear-hot-pad-disposable-hand-warmers-p184340

 

[Cloggy]

Cheers, I've just been reading about this and next time I'm going to put my camera out early and give it time to acclimatise.

 

[jimmyjamjojo]

This is a common problem in astronomy. Unfortunately acclimatizing wont help, unless you're going from cold to hot. The problem is down to the lens cooling to a temperature lower than the dew point of the night air (i'l spare you the complicated reason why). Generally, a dew shield helps delay it (basically a longer hood), but only heat will prevent it. You can buy dew straps which are basically heat matts that wrap around the circumferance, or just give it a blast from a hairdryer, you can get 12v jobbies that will run off of one of those portable car battery chargers. That might be too much kit for you, but astronomers tend to have them around for powering their mounts anyway...

 

[SLRUser]

As mentioned already, use a lens hood as a minimum and use dew heaters to prevent the build-up of dew. A hair drier will help to remove dew but it will quickly form again.

If you are not imaging the sky, point the camera downwards towards the ground, this makes the glass lose much less heat than pointing it skywards.

 

[Infinite]

Yea this is a problem use try to keep the camera and lens warm