Sorry for the late response, I was out of business some time sad.png
I had the Raspi with the changed case in use now for several sessions. I also had some concerns regarding the open GPIO pins. I solved that with a piece of foam which I just put on the pins.
Last week I had about 15°C to 20°C in the night and the Raspi was working with kstars and PHD2 guiding at 51°C. This I had with the old case during winter wink.png
Till now I had no problems also during at least two foggy nights, where the telescope was wet afterwards. I think due to the "heat" of the big heat dissipator (which coveres the whole Raspi) there was no fog on the raspi (dew heater).