I am kind of new to the list so I should introduce myself. I live in Tooele and have been into astronomy for years. I have been reading posts in the list for a while and enjoying all the great info. But now I have been bothered with a question that I can't really find the answer to. I hope someone can help me answer it. I bought a Nexstar 8" SCT about 9 months ago. I think it is a great scope but it is the first SCT that I have owned and I wonder about dew forming on/in it after I bring it inside after an observing session. I always put the lens caps on and store it inside my house when I am done with it. Now that we are getting into the cold weather season, I wonder if there might be a danger of dew forming on/in it because of the sudden change of temp and such. Does anybody have experience on this? Pau.
Hi Paul, Just offhand, my feeling is that dew is a pain in the butt when you want to use the telescope. You can use a dew shield, which in effect is an inexpensive projection that goes around the tube to prevent dew forming on the glass. Or you can buy a little warmer that goes around the end of the tube to keep it warm enough that dew won't form. I never found any use for my dew shield, however. If you're worried about dew forming on the glass once you take it inside, I never thought that was anything to worry about. It quickly evaporated. But I'm interested in what others recommend. -- Joe
Dew will for on all parts of the scope. This water will not do any good for your scope, and will eventually do you bad. My opinion has always been to leave a telescope in its case in an unheated garage or shed. That way it is at temperature equilibrium when you want to use it and you avoid the condensation. Brent --- Paul C Johnson <pjohnson@xmission.com> wrote:
I am kind of new to the list so I should introduce myself. I live in Tooele and have been into astronomy for years. I have been reading posts in the list for a while and enjoying all the great info. But now I have been bothered with a question that I can't really find the answer to. I hope someone can help me answer it.
I bought a Nexstar 8" SCT about 9 months ago. I think it is a great scope but it is the first SCT that I have owned and I wonder about dew forming on/in it after I bring it inside after an observing session. I always put the lens caps on and store it inside my house when I am done with it. Now that we are getting into the cold weather season, I wonder if there might be a danger of dew forming on/in it because of the sudden change of temp and such. Does anybody have experience on this?
Pau.
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Brent, I have been thinking about doing that. I have an LX200, and my concern is that the intense cold of winter might damage the computer or somehow freeze up the gears, if it's left at subfreezing temperatures for weeks. But I don't know. Any thoughts on that? Thanks, Joe
There is a shipping temperature specification, or a non-operating temperature spec on just about everything. Most of the electronics I have worked (ZIP, JAZ, etc.) with use -40 for this temp, although some are colder. Chuck is correct about LCD screens. I think their spec is -23 centigrade (-10F). The newer screens are specified at -51C (-60F). The electronics are very hardy and will not be hurt by low temps. The method of dew collection is radiation. The corrector/objective/anything with a view of the sky radiates its heat into space, because space is very cold. As soon as it becomes colder than the dew point, it will collect liquid or solid water on its surface. This water facilitates corrosion, and allows galvanic action to corrode. The dew/frost doesn't have to be there very long. These things happen all the time. A dew cap works because it shades the corrector/objective from space. The optical element sees mostly the dew cap (MUCH warmer than space) and will not radiate as much energy away. This normally allows it to stay above the dew point because of convection (primarily) and conduction. Things kept in a covered area such as a garage or dome don't have the opportunity to cool below the dew point in the same manner because what they see is not anywhere near as cold as the near absolute zero (3K-4K) of space. Any well designed telescope is made to be used in the cold. I would not worry at all about leaving a telescope in an unheated garage or shed, or observatory, or etc. Brent --- Joe Bauman <bau@desnews.com> wrote:
Brent, I have been thinking about doing that. I have an LX200, and my concern is that the intense cold of winter might damage the computer or somehow freeze up the gears, if it's left at subfreezing temperatures for weeks. But I don't know. Any thoughts on that? Thanks, Joe
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Joe, I've had my LX-200 out every winter for the past 4 - 5 years and have imaged successfully through all temps. I have heard the fan on my ST-7 making odd noises at really cold temps and will look at disabling in the future. I did put silicone vacuum grease on the central slider tube and low temp grease on the RA and Dec gears. I believe both of those steps are necessary. The RA will benefit from a through cleaning and re-greasing anyway, unless Meade has done better lately in cleaning out the swarf. Jim Sgt ----- Original Message ----- From: "Joe Bauman" <bau@desnews.com> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Tuesday, November 18, 2003 7:52 AM Subject: Re: [Utah-astronomy] Question about dew.
Brent, I have been thinking about doing that. I have an LX200, and my concern is that the intense cold of winter might damage the computer or somehow freeze up the gears, if it's left at subfreezing temperatures for weeks. But I don't know. Any thoughts on that? Thanks, Joe
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Very interesting, Jim! I need to look further into cleaning and greasing. Where do I start? How did you do it -- just take your telescope apart and see what needs cleaning, or find a manual about the process, or what? Thanks very much, Joe
Joe, I suggest we talk off-line a bit. A phone call would probably save a lot of time compared to e-mail exchanges. Jim Sgt At 07:00 AM 11/19/2003, you wrote:
Very interesting, Jim! I need to look further into cleaning and greasing. Where do I start? How did you do it -- just take your telescope apart and see what needs cleaning, or find a manual about the process, or what? Thanks very much, Joe
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participants (5)
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Brent Watson -
Jim Seargeant -
Jim Seargeant
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Joe Bauman -
Paul C Johnson