Dew at WSP

I am wondering how much I need to invest for dew protection coming to the WSP from dry AZ ( a record 102 days w/o rain has been just broken).
I am thinking of Astrosystem's secondary mirror heater with a temp
probe. I like it is autonomous, can be fed from a 9V battery.
Now with the main mirror having a bottom fan, do I need to be worried
of the primary mirror dewing over ?

Thanks,

David

David
I think your plans for a dew heater from Astrosystems for your secondary sound like all you will need. I have been to WSP five times. One night during the five weeks I had dew form on the primary of my 20 inch Starmaster. The rest of the time I have been fine with the secondary dew heater being all that was needed. If you have your secondary rigged for dew prevention you will be as well equipped as anybody else there.

On many nights at WSP, it is too darn windy for dew, but there have been some dewy nights. One year - I think it was three WSPs ago - we had a couple of nights of nasty dew, and 12 volt hair driers and anti-dew devices were very "hot" items at the vendor's tents. I'd be prepared.

Clear skies, Alan

WSP 3 years ago had near-perfect seeing -- seldom have
I seen such nice Airy disks in my 11" Dob. It also had
incredible dew -- everything was completely soaked.
I mean, really, you are on this tiny ribbon of land
surrounding by the Atlantic Ocean. The dewy nights
tend to be the ones with great seeing.

The Astrosystem secondary heater with the little 9v helped
for the first couple hours, but I soon had a 2" Kendrick
heater on the diagonal mirror. I've since wired it for
external 12v which gives it a little more juice.

When I got back home I installed a heater on the primary
-- about 40 resistors taped all over the back of the mirror.
I don't use it often, but its nice to have it available.
Theres a fine line between keeping the dew off and
degrading the seeing, but a little steady heat is
better than trying to evaporate dew with the blow-dryer.
Its just a couple watts. It worked quite well on subsequent
WSP and other trips. Its handy.

And do take a blow-dryer and a hefty 12v battery to
run it, just in case.