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Thanks Bob, I will keep your advice in mind when next using the QHY9. In view of the price of this camera it is surprising that a more comprehensive handbook does not appear to be available. I recently bought a relatively cheap colour (non astro) camera and it came with a very comprehensive handbook.
I drive my QHY9 with Nebulosity software which has a setting for the QHY9 whereby a temperature is selected and the camera proceeds to cool to that point. In my case the base temperature is ambient and when I set it at -25degC it appears to move down to this temperature over a period of a few minutes. Meanwhile I proceed to set up my astro gear, train the guiding and then go to the object and commence imaging - this takes about 20 mins (barring fumbles!) which should permit the QHY9 temperature to stabilize. I would hope that the camera stayed at the nominated temperature as I take darks after the imaging session. However, since the camera noise, even with 15min subs, is negligible at -25degC the use of the darks is mainly to remove hot pixels.
By the way, the apparent icing or moisture problem I see occurs progressively after the first initial good images and appears as an increasing dark band across the middle of the screen image of the feint nebulosity. This occurred when I was imaging the Carina nebula. I then tried a similar length image on a nearby star cluster where I suppose because of the relatively brightness of the stars, no evidence of the dark band was at all evident.
I guess there are two opportunities for dewing if not directly on the imaging chip, ie on the glass cover of the sealed chip box or on the additional glass in the camera nose. I have been drying the camera for a couple of days and the next time I use it if the above problem recurs I will have a look into the camera nose to see whether I can see any evidence of dewing. With my old QHY8 I recall I had to fit a small heater on the camera nose to overcome a dewing problem there. All good fun!
Peter
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