Little flowers of ice

[hes not well again]

I was out last night and in Scotland it was windy and definitely sub zero temp but very clear. As the moon was shining down with idiot good humour washing everything else out I spent an hour or so cruising the terminator  and found that after a while ice was spreading across the primary mirror of my dob. I remembered watching Sky at Night some time ago and someone on the program was saying that the most useful item in his kit was a hairdryer for getting ice of his mirror. Surely he wasn't suggesting that you should use warm air on your scope was he? Maybe he meant on the cold setting although would that have any effect or maybe make things worse. Or maybe, and I think this is most likely, I completely misunderstood what he was saying.  

[Ant]

A hair dryer is really good for clearing dew from a refractor, corrector plate or finder...

Sometimes it's the only thing that will do that job

Ant

[Mad Taff]

I haven't been out with my telescope when it's been freezing yet. Had a few cold nights though and problens with dew. I've heard that a hair dryer can fix these problems temporarily.  

[hes not well again]

i take it this is with the hairdryer blowing cold air

[Peter Drew]

No, hot air, keep the hairdryer in motion and not too close to the optics. Never caused me any problems, my hair is a different matter! 

[hes not well again]

Well you learn something every day. I had previously killed people who said this and dumped their body in the canal but now I see they have a point.

[DaveGarland]

Yup a short blast down the tube and another on the back of the mirror of a newt does the trick fine. The idea is to raise the temperature of the optics above the dew point. Don't spend long on this though as a large temperature change will create thermals in the OTA.

[reddoss]

I use a 12V hairdryer which you can by from camping/sailing  shops.

They use up a lot of juice and will drain a 7 amp hour battery in only  a few mins. However, they are much safer than 240 V, as electricity and water do not mix!

[hes not well again]

Good for up a mountain though where there is no mains