Thanks for the interesting reading all.
I usually put some argon in the body of my 9 a few times each year according to the older linked thread here.
Sometimes every 18months or so may polish the outer CCD chamber very gently. Have used Q tips and isopropanol before, but generally its so clean a puff/brush then gentle breath and polish is sufficient. Can tell from reflections of bright room light if there's anything on there before and after.
Love the 2 stage cooling on my 9.
-25 in the middle of Qld summer (when there are no clouds
)
The chamber warming circuit generally works very well, as long as you ramp up the cooling over 10-15 mins. Easy to do with modern software while everything else is getting sorted.