Emergency dew prevention: Heaters won't arrive for a week or more but skies clear tomorrow and saturday!

[pipnina]

I've done some upgrades to my scope (focuser etc) and am itching to get some first light with the improvements. Sadly, the humidity is going to be up to 95% with the clear weather coming soon, and the dew heater straps were out of stock so I still need to wait for my order to be dispatched.

Are there any emergency makeshift anti-dew measures I can take to get me through two nights? Jig a hair dryer to point at the scope? Heat up towels and tie them to the dew shield? I dunno, but it's going to fog up immediately if I can't do something : (

I have a tiny tiny dew heater that I bought for my DSLR, which could cover my guide scope, but the main scope is troubling me...

[Ouroboros]

I find a home made dew shield very effective.  I made mine from a foam sleeping mat bought from Mountain Warehouse.  I have sometimes resorted to using a hair dryer but only very very carefully from some distance from the lens or mirror. I usually only have to do this once or twice during a session though. 

[Ratlet]

Craft foam board all the way for me.  Twice as long as the diameter.  Also had great results with underlay from vinyl click lock flooring.

This is with small 72mm lenses and 58mm lenses also.  Keeps it dew free fro at least 4 hours even in high humidity up in Scotland.

Keep the hairdryer near by to give it a warm up if it does dew up.

Oh and if your supergluing crafting foam the working time before it sets is somewhere between 0 and 6 nanoseconds.

[pipnina]

49 minutes ago, Ouroboros said:

I find a home made dew shield very effective.  I made mine from a foam sleeping mat bought from Mountain Warehouse.  I have sometimes resorted to using a hair dryer but only very very carefully from some distance from the lens or mirror. I usually only have to do this once or twice during a session though. 

Thankfully the scope has an extendable shield built in, with a velour-like flocking fabric lining it. It's about a foot long away from the lens cell, but it does still fog up above 80% RH. At least the hair dryer is safe, maybe I could pack something warm in the gap between the cell and the dew shield? Not sure what to use though as water (i.e. in a flannel) holds heat but will cool down fast, and cause condensation when it does so... Maybe I can see if any shops near me have chemical hand warmers?

[jjohnson3803]

I used to use chemical hand warmer packs - held them on with large rubber / hair bands.  They worked well.

[chewie]

I use a foil camping mat cut up and taped on to the body, the foil windscreen covers you get for cars to keep the frost of are similar.