Recommendation for a reliable all night anti fog spray for a camera lens

[Jay Berg]

Thanks for your response(s)!!

[David Glasser]

Hi Jay,

I wouldn’t use anti-fog spray, like the stuff I use on my snorkel mask, on a high quality camera lens or scope objective. 

The lens surface temperature drops by radiative cooling because the sky the lens is pointed at is cooler than the lens.  When the surface temperature drops below the dew point, the lens starts to fog up.

The usual dew prevention techniques are to use a dew shield and/or a battery powered heater strap around the lens to keep it from cooling to below the dew point. Sometimes a fan can help. And keep the lens capped when not in use.

In my experience a dew heater strap and controller hooked up to a battery are best. There are a number of manufacturers. I use an AstroZap dew controller and dew strap and a 12V lithium battery.

https://astrozap.com/collections/astrozap-dew-heat-accessories

David

On Monday, October 27, 2025 at 6:31:19 PM UTC-4 Jay Berg wrote:

Thanks for your response(s)!!