Hi Phil,
You won't need a heater, there are better passive solutions. Dew forms when the corrector is allowed to cool below the dew point and there are two ways to prevent this. The old way was to apply heater straps, which ignores the real issue - that a metal OTA loses heat fast. The second solution is to add some insulation that stops the OTA cooling down - this is sufficient to keep the corrector above the dew point, and no dew.
There is another benefit too - larger maks and SCT often are affected by in internal air current that arises while the OTA is cooling. By insulating the OTA you’re blocking the flow of heat that causes this, and the result is the internal tube current is eliminated.
A simple dewcap made from just about anything will make a significant difference and it also cuts the amount of stray light entering the OTA, which improves contrast, particularly when look at objects near the moon. a piece of foam plastic and an elastic band - even string will do to hold it in place. If the dewcap extends down over much of the OTA that will do the trick very nicely. Here’s the one I use on my much larger mak - and it is fine at a cold mountain site where the temps fall below zero
https://www.cloudynights.com/topic/6.../?fromsearch=1
Coreflute is available in black 2.5mm sheets for a few dollars, in case you’re wondering.