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To cap or not?

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#1 REC

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Posted 02 May 2013 - 07:19 AM

Now that spring is here, comes the dew. Question: do you cap the SCT before you bring it in the house or leave it open to air out?

Now if it did due up outside I was told that you leave it open to let the air evaporate, but if it is cold out and you bring it into a warm house you should cap it before you come in to prevent the plate from dewing up?

Bob

#2 rmollise

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Posted 02 May 2013 - 08:16 AM

Now that spring is here, comes the dew. Question: do you cap the SCT before you bring it in the house or leave it open to air out?

Now if it did due up outside I was told that you leave it open to let the air evaporate, but if it is cold out and you bring it into a warm house you should cap it before you come in to prevent the plate from dewing up?

Bob


It's really easy:

If there is dew on the corrector, do not cap it. NEVER cover dewed optics.

If there is no dew, put the cap on. "They" told you wrong. Dew will form on the cap

;)

#3 REC

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Posted 02 May 2013 - 09:14 AM

Thanks Rod!

#4 WesC

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Posted 02 May 2013 - 12:09 PM

Since I keep mine in the garage and its about the same temp as the outside air (I leave it open while I'm observing) I put the cap on, I haven't seen any dew on the corrector yet though.

#5 cavefrog

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Posted 02 May 2013 - 10:05 PM

If my scope has not dewed up, I cap it before I take it in. after the scope comes up to room temp, I uncap to check it.
If the scope has dewed while outside, I take a hairdryer to it. when I have gotten rid of the condensation, then I will cap it and bring it in.
if you bring a scope that has dewed up outside, into the warm house uncapped , you are going to get rivulets of water running down it. and that will be much worse. but still... do not cap a dewed scope!
when my scope gets condensation on the lens (rare, because I always use heater systems, or hairdryer in a pinch), I clear it with a hairdryer, cap it, bring it inside, and commence drying the tube with a towel first because it is usually running with water, (high humidity around here) then take the hairdryer to the tube. when the tube is dry, (and warmer) I pull the cap and make sure the corrector or objective is clear.

Theo

#6 cavefrog

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Posted 02 May 2013 - 10:11 PM

ya'know, while on this subject, I think tube manufacturers should think about making tubes with a dew resistant texture on them like a lot of mounts have. My tubes always have a bunch more dew than the mount gets.

Theo

#7 REC

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Posted 03 May 2013 - 09:13 AM

Actually my new Meade scope does have a texture finish to the tube now. My ETX's are shiny blue steel tubes.

#8 Terrance

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Posted 03 May 2013 - 10:44 AM

What about situation where scope (in my case a C11) dews up outside, on covered balcony, but where it is not feasible to tear down setup and take scope inside? What is best procedure, under those limitations?

Leave out uncapped all night?
Put all-weather scope cover on but leave uncapped?
Other solutions?

#9 dscarpa

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Posted 03 May 2013 - 01:16 PM

When it's dewed up I use a hair dryer on my C9.25's dew collector and after it clears cap it before bringing it inside. I also dry off the OTA and warm up the cap. If I just leave it out on my covered patio uncapped it stays fogged up even when pointed down like Celestron recommends. David

#10 WesC

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Posted 03 May 2013 - 04:53 PM

Does anyone know if a Carbon Fiber tube has any affect on dewing of the OTA?

#11 dscarpa

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Posted 03 May 2013 - 05:41 PM

Nope. I've got the metal one. One thing to watch out for is internal dewing. It happened to my then new C9.25 on a night of building from the ground up fog when I stayed out a bit too long. Scope City took care of it gratis. My IM-715 mak is vastly more dew resistant than the SCT due to the thick corrector. David






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