An additional step to avert dew from collecting on those front glass corrector plates. The dew heater warms up that corrector plate in an attempt to keep dew from collecting there and it works brilliantly. In my case, I use the dew heater controls built into the Pegasus Astro PowerBox Micro. I consider it essential, actually. Most nights, without it, the RASA would only be good for 30 minutes or so and then it would be covered with dew and rendered worthless for any kind of stargazing.