I ran across a post by ZWO (Sam) on the Cloudy Nights forum concerning a question about sensor window fogging. Sam has obviously been following the discussion about the need for a window heater. The competition (QHY) has a heater in their camera. Previous advice from Sam on this, was that the camera sensor board would need a redesign to accomodate an internal heater. It seems they have been working on an external heater that is applied to the front cap of the ASi1600 (and other cooled ASI cameras). I have an image of it here:
http://zwoug.org/download/file.php?id=1315&mode=view
When I emailed Sam my concerns about it shorting out on my filter wheel (which my camera is screwed to directly by those short M42 male threads) he assured me they have tested it with their filter wheel, and that that clear shinning stuff is a membrane over the heater elements. If you want gap separation he suggested a 1mm M42 spacer would do the job and still provide a solid connection to the filter wheel. Sam has said in the email that the AR window temperature would go up by 10C as a result of the heater.
No word on availability yet.
I will make an assumption that the heater must be powered just like any other dew heater, via an RCA plug and separately to the Camera TEC power, otherwise the amperage required would go up and you would need some way of controlling the heater. I expect more info on that soon.