I've recently acquired a small CF triplet 90/600. I compared a few things with my ED80, similar aperture, similar FL. Besides the razor sharp optics, obviously, I was surprised to see that the scope didn't dew up on first light like the ED80 does. I have to run a dew heater on the ED80 lens and the lens cell and the alu tube do get very cold at night. In contrast the CF tube of the new refractor didn't feel cold to the touch even at 2:00am. As a result, I suspect heat/cold transfer or lack of, the glass was 'nice and warm' and dew free all night. I have also noticed the same with my C11. When I swapped the alu body to a CF tube I reused the old alu as a rigid dew shield. In turn the CF body still feels warm to the touch when the alu 'dewshield' is freezing. Again as a result the corrector plate doesn't seem to get as cold as it used to and although I still run a dew heater I don't have to run it hard. So it seems besides the obvious advantages of minimising focus shift with CF it does also have some interesting properties with
heat retention (for lack of a better term) under the open night sky? What do you make of it? Any similar experiences or am I imagining things?
