Lacerta 15 cm Long Dew Heater 3 cm wide, compatible with tubes of 40-60 mm diameter. Requires 5V from a USB power source, preferably operated from a power bank.
Anyone who has observed in the autumn-winter cold knows how much of a problem dew can cause. A dew shield provides some protection, but here is the "real" solution. Dew heaters are small heating pads or heating wires that keep optics warm. They can be attached around the eyepiece or tube using Velcro straps. Highly recommended for Schmidt and Maksutov-Cassegrain telescopes, where the corrector lens is particularly susceptible to dew, but also useful for owners of refractor telescopes.
The dew heater should not be operated from a computer as it may cause damage!