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Originally Posted by sheeny
BTW Bird, have you ever tried to measure the difference in your OTA temperature with and without the dew shield? Perhaps remove the dew shield after the scope has stabilised and see if the temp drops???
Al.
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Al, might sound a bit silly, but I don't have a dew shield, my scope is a 1.8m long newtonian monster with the secondary a fair way down from the open end so it doesn't tend to get dewed up.
I'm quite paranoid about cooling the whole scope down to exact thermal equilibrium with the air for best planetary imaging, and a heated dewshield would upset that, so I decided a while back to just avoid them altogether.
When I do get dew on the secondary I have a hand-held warm air blower (i.e. hair dryer) that removes it in a few seconds.
regards, Bird