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dew! what a pain in the?


redfox1971
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Well i been observing since last autumn and this dew seems to be a big problem nothing more annoying than setting my celestron cpc800 up to cool down couple hours with mirror cap left on then when ready i remove cap place my homemade dew shield over front,all ok for hour or two then start to see the signs of moisture,whitch means ither give up,or get hair dryer out to dry it off,now how does that work:confused: when youve left scope cool for couple hours and now your altering temp,surely make seeing bad again,so pointless for webcam or astrophotography,so decided now time spend more money again:( on dew band and controler,so to all fellow sgl members that do astrophotography for long exsposures what do you use,i see you can get just 12v dew band but is that going be enougth to control dew or one with controler better solution,il be triping over all these battry packs and wires b4 long.i bet egypt dont suffer from dew lol.

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I remember the night I was enjoying glorious views of Saturn at 350-400x through my thermally managed dob. I popped over to have a look at the planet through a fellow observers 11inch SCT.

"Dude, why are you using such low mag on it?", I said.

"The seeing is terrible tonight!", he said.

"I see you have a dewstrap keeping the dew off, where is your controller?", I said.

"Don't use one", he said

"Talk to you later dude", I said, as I headed back to look at Saturn at 400x through all that terrible seeing!! B)

I've just got back around to working on my scope after 18 months break for house moves and renovations. I've spent a lot of time on planning and install to make the scope dewproof and quick setup. With a bit of forethought, these don't need to be mutually exclusive goals. I bought the King of Dew controllers which is the Dewbuster. This thing has turned out to be so versatile its not funny! :) At order time I was able to get Ron Keating, the maker to configure it with a Temperature sensor controlled output for the secondary mirror of my dob, 6x dewstrip outputs (Finder Objective and EP, main EP, GLP, Filterslide heater, EP box heater) 1x 3v output for my GLP and finally 4x 12v power outputs. So from the getgo it was my Dew controller and 12v power distribution controller. Turns out I didn't need the secondary mirror output or temp sensor because my cooling fans and lightshield are keeping the dew off without any other help. I was going to fit a fan controller for my primaries cooling and boundary layer fans. Then a brainwave hit me and after checking the feasability with Ron its full steam ahead and the newest use I will put my Dewbuster to. The Dewbuster uses Pulse width modulation to deliver variable power to the dew heaters. Computer fans often use PWM nowadays too. By wiring the fans to the temp sensor controlled output on the dewbuster and by swapping the wires in the temp sensor cable I will now have a fan control system via the dewbuster where it sends full power to the fans until the primary temperature gets near to ambient, slows them down somewhat until finally switching the fans off automatically when the temp sensor detects the mirror is finally at ambient.

Every fan, 12v device and dewstrip is permanently affixed to the scope. With just 2 cable bundles terminated with CAT5 Network connectors, I can connect up everything, power it up and be ready to observe only about 30 seconds later than a dob with nothing installed on it.

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