dew collecting on lens at night...

ok, i shoot mainly at night and recently my lens has started to collect dew which means i cant really shoot having anything in focus etc... its not only my camera its whoever i shoot with, it all seems fine for the first hour or so (presuming due to the heat within the camera from having it in my car/ house all day) but then it just keeps on collecting dew no matter how many times i wipe it clean, any ideas on how to resolve this?

cheers

What temperatures are you ranging from day and night? Is it a sudden drop in temp or gradual? Humidity? Where are you located?

its in the uk, prob 16 -18 degrees c and 10 - 9 at night, sudden drop though its alway ok for the first hour or 2...

Are you shooting constantly or are there large pauses in the action?

You can use the lens hood, make a hole in a clear plastic bag (like a bigger shopping bag) and tape the hood to that. Then you have the bag hanging over your lens + camera, you still have access to everything.
It's the poor man's weathersealing.

Dew accumulation, after the residual heat in the equipment has left, is not at all unusual. The 'dew point' is where moisture condenses out of the air to collect on surfaces of that temperature. I can't offer any suggestions apart from using chemical heat pack draped over the lens to keep it above the dew point. Or maybe wrapping a chemical heat pack in microfiber and putting it loosely inside the hood mounted on the lens, and pulling it out to take shots for a while before putting it back in to keep the front element above the dew point!