Dew forms when a surface cools below the dewpoint of the air next to it. It's liquid water that condenses from water vapor contained in the air that's become too cold to hold it. Once your telescope's optical surface cools enough for dew to form, your viewing night is over. Wiping dew away will get you nowhere, it will just keep forming. The only answer is dew prevention. That's where the Dew Shield comes in.
The Meade Dew Shields extends the tube out past your telescopes exposed optical surface. This will dramatically slow down the dew forming process and keep you out viewing much longer. A simple and inexpensive way to extend your viewing nights.