Fog and the vast dark nebulae

It’s now dark and moonless. October weather tends to be clear. It all adds up to our final optimum astronomy opportunity before the long months of overcast and stratus statistically begin, in early November. But first, one feature of the night remains mysterious to many: It’s this season’s predilection for morning fog, dew and frost.

It’s a bit of a paradox. The clearer and drier the night, the more beautiful is the starry firmament. And yet these conditions favor fog and frost, which you’d think should be associated with dampness rather than dryness. That’s . . .

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