A Cheap Multi-Channel Dew Heater Controller

Following on from my post about DIY Nichrome Dew Heater Bands, I'm going to show you how to build a cheap and effective dew heater controller. Whilst preventing dew formation is essential to avoid interruptions to the night's imaging, we do not want to generate excessive heat as this can cause air currents in front of the telescope's optics and degrade the quality of the image.

A dew controller enables you to manage the power output of the heater bands, and also helps to conserve battery life if you are away from the mains supply. Commercial dew heater controllers retail for £70 to £100+, but I'll show you how to make a simple one for as little as £5. Please note that this device is suitable for heater bands at 12V to 24V only.

DIY Dew Heater Controller

Making Your Own Nichrome Dew Heater Bands

In my previous post about dew formation and prevention, I explained why dew forms on your imaging gear and outlined some simple strategies for combating it. Perhaps the most effective of these is to use a Dew Heater Band to keep your telescope optics just above the dew point.

There are many commercial suppliers of dew heater bands, but they tend to be rather expensive and range from £20 for a small eyepiece heater to £70 or more for a large band to heat a 36cm scope. Making your own dew heater band is a much cheaper option and for a few pounds in materials and a small amount of effort you can make one every bit as effective as a commercially bought model.

DIY dew heater bands (wrapped around the dew shields)

Dew Formation and Prevention

Unless you are fortunate enough to do your imaging in a very dry environment, you will be all too familiar with the problem of dew forming on your telescope objective, corrector plate or camera lens. As an astro-imager who spends all his time ten metres above sea-level and within sight of the North Sea, dew used to interrupt proceedings far too often for my liking.

This post explains why dew forms and what we can do to delay or prevent it.