Bringing Cold Scope Indoors

[Cypher]

I spent a good few hours outside this evening with my new scope before the clouds rolled in at which point I left the scope out in the hope the clouds would break, tipping it to point down just incase dew formed or dust settled on the tube, but at 23:00 I decided called it a night and packed up. I brought the scope and eyepieces inside into a coolish conservatory but I immediately noticed the eyepieces had fogged over when I went to put the covers back on. Checking the mirror, it looked liked something had been spilt inside it. It wasn't an all over fog but a weird streaky pattern. Panic did set in at this point, but I had read about the hairdryer being a useful accessory for dew so I immediately used the low power setting on the hairdryer to gentle warm things up and get rid of the mist on the mirror and eyepieces.

Whats the correct procedure for bring in a freezing cold telescope to the relative warmth of a cool conservatory?

[jimmyjamjoejoe]

Pretty much exactly what you did.

You can either leave it uncapped for the night, pointing down to avoid dust settling, or you can give it a quick blow dry.

Don't worry about any water marks/streaks etc. Visual pollution like that will barely affect the views from the scope. Scratches made by improper/unnecessary cleaning however, will damage the mirror coatings and possibly leave it open to corrosion.

[jfox61]

Pretty much as above I bring mine in and let the heat dissipate the fogging naturally. Takes around 20 minutes or so, then I cap them. I also do the same with ep's and filters

[Dove]

thanks for the tips ave had mine out for couple hours every night hopingthe clouds will go away. ( haven't so for)

[benjii]

The tip for bringing a digital camera in from the cold in order to avoid moisture build up when it warms, is to seal it in a plastic bag so the air warms up slowly, thus avoiding condensation. A similar method can be applied to your telescope, just cap it all up before you come in and do not take the top off once inside. After a number of hours, it'll be warmed and be moisture and streak free.

My other half likes to live in a desert like environment with the heating all set to 11 and so I have been slightly concerned bringing it in from a really cold night, however, this method has always worked perfectly for me.

[haitch]

The air outside has a much lower moisture content because it is cooler. If there is no condensation on the optics whilst it is out cap it before you bring it in. That way you keep the dry air inside and as the optics and air inside gradually warm there is virtually no chance of condensation forming.

Edit: Like Benjii says

[benjii]

That's interesting, it never occured to me that was the reason. I've just been doing it all this time because I knew it worked, ignorant of the science!

[Cypher]

Thanks for the replies, I'll cap everything outside from now on.

What causes the streaks on the primary mirror ? They scared the hell out of me. LOL

[Carbon Brush]

This may be of interest.

http://stargazerslounge.com/beginners-help-advice/178817-bringing-cold-scope-inside.html

[Cypher]

thanks David, pretty mixed bag between capping and not capping. I think I'd jump into the capped camp after seeing the mirror last night within seconds of entering the house. I think it has to be best to not let the moisture form in the first place.

What position is it best to store the reflector after bringing in from the cold ? I've left mine stood on the mirror end but I'm now wondering about keeping it horizontal to allow any moisture that may build up to run off.

[haitch]

It's basic science - warm air can hold more moisture than cold. When warm air hits the mirror it instantly cools and the moisture condenses out. If you trap the cold dry air from outside in the scope it will never be able to hold less moisture as it warms up so won't cause condensation.

Leaving it open is the solution once you have caused the problem but why cause the problem in the first place?

If you have space store it horizontal - it also reduces dust gathering on the mirror. Of course glass is actually a super cooled fluid not a solid and will eventually run to the bottom but you'll probably be long gone before then.

[jfox61]

The tip for bringing a digital camera in from the cold in order to avoid moisture build up when it warms, is to seal it in a plastic bag so the air warms up slowly, thus avoiding condensation. A similar method can be applied to your telescope, just cap it all up before you come in and do not take the top off once inside. After a number of hours, it'll be warmed and be moisture and streak free.

My other half likes to live in a desert like environment with the heating all set to 11 and so I have been slightly concerned bringing it in from a really cold night, however, this method has always worked perfectly for me.

However, this method won't work if you have already picked up dew. Putting it in a bag with dew formed, will basically just trap the moisture in the bag. Neither method is right or wrong.

It depends on the condition of your lenses before you bring them in. If they are already dewed then letting the moisture dissipate naturally is best. If they're dry then cap them or not, it's up to you.

If dew or moisture does form indoors then leaving them uncapped to let it dissipate will not harm you lenses anyway. Wiping then dry WILL.