What The Dewce?

[StevieO]

My SW 100ED refractor is as prone to dewing up as any other scope.

Not wanting unless absolutely necessary to drop a load of money on a dew heater and controller, I was today browsing round a National Trust shop and found a pair of nifty hand warmers, each encased in a miniature fleece, which work on some principle of a viscous liquid which crystallises when you press a little button and gives up heat. Reusable by  throwing into a pan of boiling water. The leveling of 'warming', though not controllable, is quite mild. They are 3 quid  a pair. I bought 2 pairs.

So I thought, Hey, I could attach these to the outside of my scope just by the objective lens, insulate them further with some bandage,and the mild warmth will conduct through the tube and lens, keeping the dew at bay.

My questions:  Is this a good idea?  Has anyone done this and what happened? Am I trailblazing a brilliant new money-saving scheme or merely re-hashing an old idea which has been tested and discarded long ago?

Cheers

SteveiO

[bobmoss]

It will work, but only up to a point. The problem is that you don't want to get the optics and tube too warm, otherwise you start inducing air currents and turbulence which affect your seeing. However, you may as well give it a go, it can't do any harm!

Don't forget to report back and let us know how you get on.

[Astro Imp]

Nice bit of lateral thinking Steveio, let us know how it pans out.

[StuartJPP]

No need to drop a load on a dew heater and controller...plenty of plans out there to make your own. I bought all the bits for a few off eBay for less than a tenner...

I don't bother with a controller...just more things to go wrong. I aim for about 3 watts, barely warm to the touch. Haven't had any problems even after a whole night of imaging in very dewy conditions.

No problem using what you have just got but a bit unpredictable not knowing when they are going cold...they should help nontheless.

[Gina]

I had plans for a fancy controlled dew heater system but when it came to it I found a simple fixed dew heater was quite adequate.  So having designed and posted about my "Rolls Royce", super-duper dew heater control I've abandoned it and adopted the KISS principle

[Adrian]

I had plans for a fancy controlled dew heater system but when it came to it I found a simple fixed dew heater was quite adequate.  So having designed and posted about my "Rolls Royce", super-duper dew heater control I've abandoned it and adopted the KISS principle

Who are you, and what have you done with Gina? 

[StevieO]

After weeks of cloudy skies I finally had the chance to try out the handwarmers....and they didn't work particularly well. The heat dissipated very quickly despite being insulated by a couple of pairs of (clean!) old socks wrapped round the scope.

So my rather pathetic attempt at saving a bit of cash has come to nothing, as I knew it probably would, given the money-black-hole nature of this great hobby. Have now bitten the bullet and ordered dew heaters for main and guiding scopes, as well as a second power tank.

Buddy, can you spare a dime?

StevieO

[Merlin]

Your dewshield might be too short. I make mine three times longer than the aperture. Also, it helps to point the refractor downwards if we are not looking through it for any length of time.

These suggestings are not a total cure, but they do help.

[michaelmorris]

After weeks of cloudy skies I finally had the chance to try out the handwarmers....and they didn't work particularly well. The heat dissipated very quickly despite being insulated by a couple of pairs of (clean!) old socks wrapped round the scope.

So my rather pathetic attempt at saving a bit of cash has come to nothing, as I knew it probably would, given the money-black-hole nature of this great hobby. Have now bitten the bullet and ordered dew heaters for main and guiding scopes, as well as a second power tank.

Buddy, can you spare a dime?

StevieO

I know they are expensive, but they really are worth it.  I've had dew heaters for 6 years now and the only ocassion when I've lost even a minute to dew was the evening I hadn't plugged the dew heater in properly.