The fogging issue can happen when condensation occurs because of extremely high relative humidity or sudden temperature changes. In the last 10 years I have had 3 or 4 similar complaints and I have spent time on this issue personally because I am an avid hunter and understand the concern. I have been using the anchor sight technology for at least 20 years and I don’t miss many days in the field during archery season. I can only remember a few times when fogging became an issue severe enough to prevent me from using it and if I had been using a peep sight all of those years I’m sure there be many more times I would have lost a shot opportunity due to low light conditions or string twist.
Having said this, there are several things one can do regarding fogging or rainy conditions. Personally I don’t hunt in the rain because you can’t track animals and like many hunters I learned that lesson the hard way. I have experimented in marginal conditions with covering the Anchor Sight with a plastic covering which can easily be made with household items and simply plucked it off before the shot. If I were hunting in high humidity, Misty conditions which could possibly cause extreme fogging I would consider breaking open a hand warmer packet, activate and stick it in my pocket. If needed, you would simply hold it around the lens area of the Anchor Sight until clear, usually within 30 seconds.
But again, I don’t want to make this sound like a serious issue because compared to a peep the anchor sight is many times more likely to function properly when needed.
There is one other point I would like to make which works for me. I hunt from the ground and can always find a natural blind somewhere within 20 yards of the trail so I practice from a sitting position at 23 yards. I can go out and sit on my pail with total confidence that I can put the arrow within the kill zone, first arrow, without using the Anchor Sight because I have developed a feel for the shot due to the exact replication made possible by using the Anchor Sight. In a hunting situation I will always consult the Anchor Sight because it will tell me I may be too nervous and shaky to make the shot. I had this happen a few years ago when drawing on a large Buck and I took a few extra seconds to settle in and steady myshot resulting in a clean kill.