Thanks for the links, Jay! -- Joe ________________________________ From: Jay Eads <jayleads@gmail.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Monday, November 7, 2011 6:57 PM Subject: Re: [Utah-astronomy] Dew/Frost prevention I've posted this link and I still think this is the best alternative: http://www.dewbuster.com/heaters/heaters.html I've made several of these and bought a Thousand Oaks controller for $109.00 plus $10.00. They've worked in the backyard though I had to replace some parts that were bad on one part. There is also the 12 volt hair dryer. From what I've read online they barely heat the air but that is all that is needed. Here is one for $18.00 plus $10.00 shipping. I picked this one because the handle doesn't collapse and that seems to be an issue for how well one of these last. http://www.amazon.com/Hand-Held-Shield-Defroster-Dryer/dp/B004MAV24C/ref=pd_... Then again, I could use my Coleman SportCat Heater http://www.walmart.com/ip/Coleman-SportCat-Catalytic-Heater/13228604 so the heat it generates just floats up if I place it near the scope. On Mon, Nov 7, 2011 at 6:11 PM, Chuck Hards <chuck.hards@gmail.com> wrote:
OK, my word isn't good enough, so here's an explanation written in nerdese:
http://home.comcast.net/~astrophoto/Articles/Dew.htm
It's on the Web, so it MUST be true.
All you have to do is warm the optics above the dew point. That temperature varies dependant on humidity. You don't need "warm" optics to prevent dew or frost.
In most cases, the optics are still cool to the touch.
Mat is on the right track with his dew chaser project. Those of you who are in need should seriously consider attending his next ATM session. A properly designed dew chaser won't consume a lot of current, but will add hours to your observing/imaging sessions when the relative humidity is high.
When my work schedule allows, I'll search the S&T archives for some articles they've printed over the years on active and passive dew/frost prevention.
I think I get a few days off in late December. :-(
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-- Jay Eads _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php