Is there a way, by looking at the weather, that you can predict whether it's going to be a dewy night?
Last night I had a friend over who wants to buy a scope, and it was the most horrendous night for dew. There was so much moisture in the air that we gave up after not very long.
Many of the weather websites will give you the current dew point temperature. Its just a matter of if the temperature will drop to approach that dew point.
The spreadsheet attached gives dew point as a function of relative humidity and temperature, both of which can be measured easily. The yellow zone is dewpoints between 10° and 5° below the actual temperature, the green zone is 5° or less - in the green zone things usually get wet...
I find it dewy if i have had rain recently and the sky is clear, warm days followed by cool late afternoons, or if the grass feels moist after the sun has set. Thats normally how i tell at home! Other times i notice that if its clear and there is a slight breeze then i get a high level fog, once it comes over it brings moisture with it!
