USB Lens Warmer, Lens Defogging Heater Condensation Prevention Lens Warmer, Fast Warming for Universal Camera Lens,Telescopes,Coffee Cup,Baby's Bottle

I haven't tested outdoors in the cold but I placed a Casio watch with thermometer and after about 10 minutes it reads over 125F. I don't see why this shouldn't work to warm a coffee mug on a long trip. I also own a 6" telescope, although it may not wrap around it I will give it a try as dew heater. Oh BTW, also works for my tennis elbow pain. Excellent!

This little thing works just fine. Has some frosty nights of astrophotography and this kept the lens nice and clear. It seems to draw current just fine from a usb port or usb charger. Also put on my 102mm telescope. I think that might be the max diameter that it will fully wrap around.

It works get on telephoto lens. 18-55, 70-200. It's a little wide for shorter fixed lens.Does the job! I like it.

Does the job. I take pictures or the night sky. Dew is a problem. I used this on a small telescope also (70mm refractor) and it’s just big enough. I attach it to a small USB power bank.

This worked this past Christmas up in Fairbanks Alaska in -50 degrees below zero. Lens did not fog or ice up while out taking photos.

Too small for a lens heater and the cable is too short, but works really well for a spot heating pad.

I use this on various canon lenses and an Evostar 72ED telescope. I never have problems with dew.

Small light weight, easy to fit in my bag. Perfect for shooting timelapse and star trails on those coolers nights.