Took my telescope to Cherry Springs and fog ruined everything

I drove 3 hours to Cherry Springs State Park last Saturday, set up my 8-inch Dobsonian, and got about 20 minutes of viewing before a thick fog rolled in. The whole sky just vanished, and my mirror started fogging up too. I had to pack it all up and sit in my car for an hour hoping it would clear, but it never did. Has anyone found a good trick for preventing dew or fog on a big mirror in humid conditions?

2 comments

2 Comments

xena_murphy22d agoMost Upvoted

@charles_wilson, have you found a 12v hair dryer works better than just a dew heater strap on the mirror cell itself?

charles_wilson22d ago

Man, that is a brutal drive to get fogged out. I've had that exact same thing happen at Cherry Springs, it's like the valley just breathes out moisture some nights. For a big dob mirror, you really need a 12v hair dryer or a dew heater strap wrapped around the back of the tube near the mirror. A simple 12v portable hair dryer from a hardware store will clear that mirror in seconds without having to take the scope apart.