Jump to content


Dew prevention?

  • Please log in to reply
1 reply to this topic

#1 James Cunningham

James Cunningham


  • *****
  • Posts: 3306
  • Joined: 07 Aug 2010
  • Loc: Maryland

Posted 18 June 2013 - 09:36 PM

Last night was really dewey here on the East Coast. By the time I went outside, there was already dew forming on the cars. I turned on my dew heaters and then it occurred to me that it might be a good idea to turn on the dew heaters even before I go out side so that dew does not even have a chance to form on the warmer equipment. Is this a good idea or do I suffer the risk of thermal waves inside the scope? Besides dew shield and dew heaters, is there anything else that can be done to prevent dew from forming on the scope and eyepieces? Thanks.

#2 star drop

star drop

    contra contrail

  • *****
  • Moderators
  • Posts: 74158
  • Joined: 02 Feb 2008
  • Loc: Snow Plop, WNY

Posted 18 June 2013 - 10:30 PM

A little preheating won't hurt. Keep your eyepieces in a case and use the "only one eyepiece out at a time" method. Observing from under a patio umbrella, porch overhang, open garage door or through a tent door can cut down the incidence of dew. It depends on the size of your telescope and the thermal mass of the protective structures. Sometime this adds a few thermal waves but it never hurts to try, especially if your dew heaters quit or have a hard time keeping up. Observing near a line of trees can also work but then one risks the chance of extra pollen or gooey stuff dripping down with the dew.

Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics