Those eBay dimmers work well for controlling heater strips (I have the more upmarket $13 version
), but they may not be suitable around imaging rigs. They dirty up the power send out a "pilot tone" around 400Hz across most of the adjustment range. When I ran a heater strip through it connected to a Celestron Powertank, the Powertank's built-in FM radio just played that tone
Cheers
Steffen.