Hi N,
I think if I had a permanent outdoor pier/mount setup then I would go for something like an inverted hard cover like a strong plastic bin, which could be sealed (or not-
perhaps vented via a filter medium) from below. Inside the bin, wrap the mount head in a thick towel/s as a secondary barrier to any moisture forming on the mount surface (due to high dew point air & lower mount surface temp)
I would also try and choose a HARD bin/cover
or modify it so that it would not trap water in any way on its outer or inner surfaces, so I'd use a hard bin/cover with a slopping or domed top and a lipless or modified rim seal area, not because it's absolutely necessary, just because it's better....
Actually any water around the rim seal area could potentially be drawn or leak in so better to avoid that by design if possible.
Here is a previous thread with many ideas discussed.....
http://www.iceinspace.com.au/forum/s...ht=rubbish+bin
Best
JA