As I am located in the New Forest, you can imagine that for some months of the year, particularly from late September until late November, condensation is a major problem in the dome.
I have always used a product called “Water Eaters” from Lakeland Plastics [I prefer the name “Water Snake” but I guess the marketing people at Lakeland didn’t] around the gap where the dome rotates. This product is basically a sausage-shaped piece of fabric filled with some water absorbing substance [possibly silica-gel].
I always place these in the gap around the dome edge [on the inside of the dome] after an imaging session and they keep the ingress of water vapour right down. Unfortunately, on their own they are still not enough!
I had a problem with the Hyperstar a couple of years back where halos started appearing around bright stars after about half an hour or so of imaging. At first I thought this was atmospheric water vapour. After quite a bit of investigation I found out it was actually water vapour in the Hyperstar itself – not good!
I got rid of the trapped water vapour by placing the Hyperstar in an oven at 40C for about an hour, but I clearly needed to also do something about protecting the observatory.
To this end I bought a dehumidifier which now runs full-time in the dome. I typically need to empty the water container every three days [roughly a gallon I suspect] throughout the year.
I also have a thermostatically controlled greenhouse heater in the dome which is used to keep the dome temperature a few degrees above freezing during the winter months.
So far, these precautions seem to be working – I’ll find out this coming winter 🙂
Have you had similar problems? If so, how have you deal with them. Drop me a line and let me know.