Techniques on keeping lens dry during long exposure?

[masayako]

Hi there,

Anyone can provide some techniques on keeping lens dry during long exposure?

Last night I play with my 16-35mm and stayed outside for over 2 hrs to take long exposure star trails pictures. The front element of my lens start to collect dew since it's quite cold... how to prevent dew in cold weather? Any help is appreciated.

Thanks!

[Courierman]

leave the lens in a cold place before you go out side , so the lens is already cold so no dew

[wimg]

Originally Posted by Courierman

leave the lens in a cold place before you go out side , so the lens is already cold so no dew

With dew it is the other way around. Dew condenses on cool objects, when the temperature gets below the dew point..

IOW, keep the camera warm -> no dew.

Kind regards, Wim

[nardes]

To prevent atmospheric moisture condensing on the objective lens of telescopes, most amateur astronomers use dew heater strips wrapped around the lens cell. These are low powered electrical heaters and you can also wrap them around the barrel of the lens just below the lens hood.

These keep the air temperature around the lens just above the ambient air temperature and so dew will not condense on the lens. They do require power, either from a battery (car type) or mains adapter.

Here are some examples from AstroZap and Dew-Not.

http://www.astrozap.com/pages/dew-strap.htm
http://www.dew-not.com/dew-not-desc-01.htm

Cheers

Dennis

[masayako]

Thanks alot. Will look into it.

Originally Posted by nardes

To prevent atmospheric moisture condensing on the objective lens of telescopes, most amateur astronomers use dew heater strips wrapped around the lens cell. These are low powered electrical heaters and you can also wrap them around the barrel of the lens just below the lens hood.

These keep the air temperature around the lens just above the ambient air temperature and so dew will not condense on the lens. They do require power, either from a battery (car type) or mains adapter.

Here are some examples from AstroZap and Dew-Not.

http://www.astrozap.com/pages/dew-strap.htm
http://www.dew-not.com/dew-not-desc-01.htm

Cheers

Dennis

[PM01]

Having the lens hood on helps a little bit. Also, the dew heaters help quite a bit but don't crank up the heat too much on them as it will change the focus point. Might not be critical on a wide angle though, but on a telescope it makes a difference.