To keep dew off a larger sized ep when leaving it in the focusser for a while slip a neoprene (wetsuit material) stubby/can cooler over it - preferably a DRY unused one.
They fit the Orion Stratus / Baader Hyperion / Vixen LVW ep's close enough to stay in place but loose enough to slip on and off. Try to get a cooler that doesn't have the smal "drain" hole in the bottom.
(I actually carry 2-3 coolers in my obs gear now for just this purpose - and another to actually keep the coke cold!)
