condensation

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condensation

Postby cwardlaw » Sun Jan 17, 2016 7:56 am

Any simple advice on caring for my telescope and protection from condensation on the outside of the lens?? Should I wipe it with anything before putting the cover back on?
Thank you
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Re: condensation

Postby Gfamily2 » Sun Jan 17, 2016 12:52 pm

I believe the general advice is that it's best not to wipe condensation off the lens. It should be pure water, so should evaporate cleanly. In practice of course, you may get some deposits, but it takes a lot of stuff on the lens to make a real difference.
You can make up a mixture of isopropyl alcohol and distilled water (both of which can be bought on ebay) and use it to carefully clean lenses about once a year, but it's not essential.

It is worth getting or making a dew shield - as that makes a real difference to the amount of condensation you get while observing. I put the objective cover on before bringing it back indoors to try and keep condensation off the objective, though I do wonder whether that condensation causes any harm.
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
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Re: condensation

Postby Aratus » Sun Jan 17, 2016 1:51 pm

I agree with all of that. There are also various 'anti-dew' systems out there that slightly warm the glass above dew point temperature while being used. If for some reason the glass was already fogged, I used a hair dryer to run warm air over the glass, once inside. Wiping the glass can smear contaminants, and could scratch the surface. It should be a very rare event!
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
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Re: condensation

Postby dave.b » Tue Jan 19, 2016 12:13 am

As for recapping it; it's best to let it air dry first as trapped moisture encourages both corrosion and mould growth.

Dave B.
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Re: condensation

Postby Aratus » Wed Jan 20, 2016 2:24 pm

To reduce the chances of dew forming on the lens try to point the telescope at the ground or at your house when you are not actually using it. The surface temperature drops partly due to the temperature of whatever is facing the surface. A clear sky is very much colder than a house or the ground. It sounds a little weird but the physics is quite sound.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
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