Quote:
Originally Posted by rat156
Hi All,
What does everyone do about focus shift at this time of year. Today was low-mid 30's here in Melbourne. It's nice and clear tonight, big moon, but OK for some narrowband imaging. The ASA N12 take quite a while to cool down, I have just achieved stable focus at about 2330, which leaves little time for imaging before the sun rises again tomorrow morning.
Other than putting a cooler in my observatory what can I do? I know that Bert has some fancy temperature control stuff on his fast scope, but I'm hoping for something simpler.
I have been focusing between subs, but the focus shifts during 15 or 30 minute exposures enough that I get sub-optimal star shapes.
Cheers
Stuart
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In summer I have been opening the observatory dome about 30 -60min
before the sun sets which gives me 2-3hrs of cooling before imaging starts and I run the AG12's three mirror cooling fans (which suck the air out of the tube rather than blow on the back of the mirror) from dome open to camera shut down, all night.
Mike