Dewing up!

[conura]

Hey all,

First off, thanks for all the help so far! My 8" Dob is set up nicely with your help and I think it's (adequetely) collimated. I presume this because Stars seemed pretty sharp and when I unfocused them they seemed to be very close to a perfect circle!

Last night I spent about 90 minutes looking at Jupiter, probably very boring to most of you guys but I was very very impressed! At times it would become more clear and I could see a LOT of detail, and the moons etc. Beautiful! The moon was also very impressive, I felt like I could see into the craters!

Annyway, after a few hours the scope started to get covered in dew. I (stupidly) used a soft tissue to clean the secondary mirror, however after some reading into mirror maintenance realised this was a very stupid idea..Luckily I didn't scratch it! Anyway, what do you all do when the scope starts to dew up? Is it time to just give up? Finally, when I take it in it's often very wet from the cold/damp air..I understand that the scope is made of pretty simple materials (metal and glass by the looks of it), presumably it doesn't need to be thoroughly dried, but I wanted to check as I'd like it to last a long while!

Thanks all

[Questions]

Well you could buya dew shield for £20

or

DIY Cheap Dew shield

Camping mat £5

stickbacky velcro strip £2

(from everyones favorite auction store)

Make a tube thats about twice the length of the scope aperture, velco it up and away you go. It will also help with unwanted light pollution.

[MartinB]

And if that doesn't work a gentle application of hair dryer through the drawer tube. If the primary dews up then a heftier blast straight down the tube.

[conura]

Got it, hairdryer it is! A friend managed to get a finger print on the secondary which I used a very soft tissue to clean - Will this have done any damage to the mirror? There is nothing that I can see but am worried I have somehow impacted my view quality! I am probably over worrying!

Cheers

Con

[brantuk]

A dew shield is a good idea - you can also get "elasticated strap" shaped dew heater bands that run off a controller and good battery, if the problem persists.

When you bring it in - keep it horizontal or pointing down a little so any moisture drips out of it rather than onto the primary

[MartinB]

Got it, hairdryer it is! A friend managed to get a finger print on the secondary which I used a very soft tissue to clean - Will this have done any damage to the mirror? There is nothing that I can see but am worried I have somehow impacted my view quality! I am probably over worrying!

Cheers

Con

Very unlikely to have caused a problem Con but best not to do it on a regular basis!

[conura]

Thanks all

[Martin-Devon]

A dew shield will certainly help but it's still probably not enough. Last night I had my scope outside starting at 6.30pm - even with a Celestron dew shield, by 9.30pm the secondary mirror was absolutely covered in dew. I'm sure the shield slowed it down (since my Telrad dewed up in 30 minutes), but I'm beginning to think that only dew heaters are going to be the long-term answer. I've recently ordered the Orion dew zapper strips; let's hope this does the job