Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Bringing the scope back inside

  • Please log in to reply
10 replies to this topic

#1 daslolo

daslolo

    Vostok 1

  • -----
  • topic starter
  • Posts: 162
  • Joined: 18 Jan 2020
  • Loc: Camano Island, WA

Posted 20 February 2020 - 01:28 AM

I am lucky to live in the middle of nowhere so when the sky clears up I move the ultra light lx65 to the front of the house, 10 minutes later it's ready to go (25 minutes when Audiostar decides to show off its bugs)

 

Night of viewing (cold), feeling tired, bringing the scope back inside (warm). Dew forms, an hour later when I check dew is gone.

 

Is it damaging to the scope? I can put it in the garage but I like having this object in the house, it's pretty in an industrial sort of way.

 

I read a year old old thread on the subject that didn't converge to any consensus.

 

Is there now a consensus?



#2 msl615

msl615

    Viking 1

  • *****
  • Posts: 769
  • Joined: 07 Jun 2015
  • Loc: Fairbanks, Alaska

Posted 20 February 2020 - 01:40 AM

When I bring my scopes in from the cold  (down to -25F or so into a warm house), I will wrap the OTA up in a polarfleece blanket, or a cloth "game hunting  bag" so that they are not directly exposed to the warm-humid air inside the house. Been doing this for  years with no side effects. 

 

Mike 


  • Paul Schroeder, Bean614, cookjaiii and 1 other like this

#3 B 26354

B 26354

    Apollo

  • -----
  • Posts: 1,203
  • Joined: 05 Jan 2017
  • Loc: Southern California semi-desert (NELM mag 5.3)

Posted 20 February 2020 - 02:18 AM

Not sure exactly what scope you have (in  your signature, listing your major pieces of equipment -- and your location -- is hugely helpful when members are attempting to answer questions)... but an old "rule of thumb" is to keep your cold optical instrument un-capped when bringing it inside, until the dew has dissipated.

 

Leaving a cold optical instrument capped traps the moisture which forms on the optics... which, if repeated over a prolonged period of time, promotes the growth of fungus on the optical surface(s).


Edited by B 26354, 20 February 2020 - 02:36 AM.


#4 daslolo

daslolo

    Vostok 1

  • -----
  • topic starter
  • Posts: 162
  • Joined: 18 Jan 2020
  • Loc: Camano Island, WA

Posted 20 February 2020 - 02:19 AM

Love it! It makes so much sense I'll do that tonight.

 

-25F brrr, Alaska clear skies?



#5 james7ca

james7ca

    Cosmos

  • *****
  • Posts: 8,009
  • Joined: 21 May 2011
  • Loc: San Diego, CA

Posted 20 February 2020 - 04:10 AM

If you bring a cold telescope inside to a warm and more humid environment you will get water condensations on everything that is exposed to the inside air (mirror, lens, everything). So, don't do that. What you want to do is to prevent the warm and more humid air from contacting (directly) the cold object. So, while the scope is still outside place it into some form of air-tight container or bag that contains as little excess air as possible and then seal the container or bag. Then bring that inside.

 

Then, after several hours and after the scope has reached the indoor temperature open everything up and expose it to the indoor air.

 

The only exception to this "rule" should be when the scope is already wet and in that case you need to dry it or allow it to dry BEFORE you bring it back inside. How you do the latter is your own concern, but if the mirror or lens has any condensations on it then it's probably best just to leave the scope outside in a protected location, best would be in an unheated but dry garage or storage shed. If you can't do that (for either safety concerns or because you don't have such a structure) then do your best to dry the optics and optical tube and then use the guidelines I gave above. I sometimes use a small and low-power defroster device that is designed for use in a car, from a 12VDC source.

 

Now, if you know that the humidity inside is so low that there would be no possibility of condensations on a cold object, then you can just bring the scope directly inside without waiting or enclosing it in a container. However, you'd still want to try to dry anything that was already wet before you do that and I'd be very careful about assuming that the indoors is dry enough for this kind of treatment (it probably isn't the case in most homes unless you use dehumidifiers or live in a location where the humidity is in the single digits -- both outside and inside).


  • jimandlaura26 and cookjaiii like this

#6 astrofun

astrofun

    Lift Off

  • -----
  • Posts: 21
  • Joined: 05 Apr 2010
  • Loc: Central BC

Posted 20 February 2020 - 08:30 AM

Hi Daslolo,

I keep my cases outside with me, closed so they don't get frost or dew inside, so they are at ambient temperature with the scope, eyepieces, accessories etc. At the end of a session I put the caps back on the scope and eyepieces and put everything with dew or frost on them into their respective cases and close them up.

Put them back in the house and leave them closed up. As long as they are closed up no more moisture will condense on them from the warm moist air of the house. The next morning or when everything has equalized to room temperature open everything up and let the little bit of moisture from any dew that may have formed from the night before evaporate. I have been doing this for a couple decades and have had no moisture damage to my equipment. I live in central BC Canada and often observe in temps down to -20 C.

Doug


  • daslolo likes this

#7 treadmarks

treadmarks

    Apollo

  • -----
  • Posts: 1,048
  • Joined: 27 Jan 2016
  • Loc: Boston MA

Posted 20 February 2020 - 01:38 PM

It depends on the material used. Repeated cycles of temperature changes could result in cracks forming, or cracks expanding via thermal expansion.

 

I know that, at least for Celestron SCTs, they use a Pyrex type glass for the mirror, and that's pretty common throughout the industry. One of the specific reasons for this is that it handles thermal expansion very well. So I'd say telescopes are generally pretty good about handling temperature changes. Of course, there are limits to everything, but don't ask me to remember the exact limits of a specific type of glass.



#8 msl615

msl615

    Viking 1

  • *****
  • Posts: 769
  • Joined: 07 Jun 2015
  • Loc: Fairbanks, Alaska

Posted 20 February 2020 - 01:39 PM

Yep....I want to back up the message from Doug above in  BC.  When  I talked before about wrapping the scope in bags or polarfleece, that is only if I don't have a case for them. Following Doug's process, my small MAKs have cases, so  those come outside with me and the OTA. If I am taking the scope off of the mount, then it goes into the the cold case, the case is sealed and then entire assembly is brought back into the house. 

 

Mike


  • SeattleScott likes this

#9 daslolo

daslolo

    Vostok 1

  • -----
  • topic starter
  • Posts: 162
  • Joined: 18 Jan 2020
  • Loc: Camano Island, WA

Posted 20 February 2020 - 06:48 PM

Signature added

yesterday i capped it and covered it with a camping bag then i left the bag cool down for a few hours then brought it back in
I'll glue a tiny camera inside the cap to see if dew forms  



#10 kevint1

kevint1

    Viking 1

  • *****
  • Posts: 794
  • Joined: 19 Apr 2011
  • Loc: West Michigan

Posted 21 February 2020 - 07:55 PM

I bring my scope and eyepieces outside in their cases and when I’m done for the night I pack everything back in their cases before I bring them inside the house. I leave them in their cases and let them warm to room temperature overnight. I usually just leave them in their cases until my next observing session. I’ve never had any dew or condensation or fungus problems with any of my scopes or eyepieces.

 

When I brought everything in last night it was 8* F. I just set up for tonight and the scope and eyepieces are dry. Neither my scope or eyepiece case are air tight, they do need to breathe some. I use Pelican cases for my eyepieces and have removed the rubber “O” rings to let them breathe. 


Edited by kevint1, 21 February 2020 - 07:56 PM.

  • punk35, astrofun and daslolo like this

#11 punk35

punk35

    Apollo

  • *****
  • Posts: 1,392
  • Joined: 26 Jan 2005
  • Loc: Adrian Michigan

Posted 21 February 2020 - 09:06 PM

I take my scope and ep cases out and leave them in the back of my wife’s suv. When I pack up the cases are the same temp as the equipment. I take them inside and just let them sit for a day. No problem so far. I don’t think I’d do this if the scope was actually wet/covered in frost. 




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics