Joe, Chuck here. Dew is prevented by keeping whatever you're interested in keeping dry at a temperature above the dew point. This is never warm to the touch under most conditions, just not quite as cold as ambient temperature. In the field, a "dewcap" prevents objectives (or corrector plates) from chilling too quickly. To extend this time, extend the dewcap. 1-1/2 diameters is standard. The best coverings are "breathable", impermeable plastic only serves to trap moisture inside. Mylar covers are for daytime, dust protection only. Some "experts" have advocated keeping a bowl or cloth bag of silica gell crystals inside telescopes stored outside, and heating the crystals in the oven every few weeks to dry them out. Personally, in 35 years of observing, I've had a problem with dew exactly once, and that was with a scope left on the lawn all night. Scopes in sheds or observatories will not accumulate dew unless they are colder than ambient temperature; not really possible after the roof or slit closes up. C. --- Joe Bauman <bau@desnews.com> wrote:
Quite informative, Dale. How cold do you think the computer part of the telescope gets? And what if I left my LX-200 in a shed with plastic bags completely covering it? Thanks again, Joe
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