Severe humidity fogging up my mirrors and eyepieces

[cpittman35]

Hey guys. I finally got my telescope, Celestron astromaster 130eq, out on the back porch tonight. It's been raining and cloudy since I got it last week.  

Long story short within 10 minutes of me being outside the entire scope basically turned into a dripping mess from the humidity.  Super cold inside the house and nasty wet heat outside don't mix well. Humidity in South Alabama is just a way of life. 

My question is how can I combat the fogged up mirror and eye pieces?  I keep seeing folks post about letting the scope cool down before using it. What does that mean? 

I was able to see Mars with my 2x Barlow and 6mm lens briefly before the mirror fogged completely up. 

Thanks in advance for any help and advice. 

Oh and the reviews were right. The starfinder red dot is pure garbage in my eyes right now. Until I figure it out of course  I spent all week tweaking it and getting it aligned...... So I thought. 

[Ruud]

Hi C.

When the telescope is warmer than ambient temperature, thermal plumes rising from the mirror can disturb the image, and, especially on humid nights, when the mirror gets too cold it may dew over. 

There are passive as well as active measures you can take to prevent dew. See here to get an idea. Of course not every night is equally humid. If you want to keep track of the humidity, seeing, clouds, temp etcetera in your area, you can use something like this amateur astronomy forecast: Meteoblue for Mobile.

I quickly gave up on the Celestron red dot finder. I now use a better one on my goto (identical to this one, but with a different brand name and cheaper). For manual star hopping I prefer an 8x50 RACI.

Happy observing ... 

[Dave In Vermont]

Letting the telescope reach ambient temperature involves bringing it outside about an hour before you plan to use it. This helps stabilize the image you see through the eyepiece by reducing tube-currents that arise by cold and hot meeting in the tube - making the view 'boil' like the puddes of water you see as a mirage down a highway in summertime. For humidity and condensation problems, people employ a dew-heater if one is needed, situating such depends on the scope. A cooling-fan for the primary-mirror may be something for your situation.

I'm sure others will post other ideas for you and the Alabama-weather.

Dave

<EDIT> Ouch! Ruud! Your on my right foot!

[Stu]

Sounds like you have the reverse problem to us over here ie you need to let your scope warm up before using it! Basically you need to let it reach the same temperature as it is outside before it will give good images. Once it reaches that temperature the humidity problem should reduce or even go away.

Here is my suggestion..... Find a way of putting the scope outside in a moisture proof container to stop it dewing up while it reaches ambient temperature. That could be a watertight storage box or even just a sealed plastic bag. Leave it outside for an hour then take it out and pop it on the mount and see how you go.

[Riemann]

Hi

You have already been given the best advice - let the scope and eyepieces warm up before use, protected from condensation whilst they are doing so.

As a crude back-up you could try a hairdryer on a cool setting to clear the secondary mirror and eyepiece if you are still getting fogging during a viewing session.   However, each drying may only buy you a few minutes if your humidity is very high.

Dealing with the primary mirror requires a dew heater if pre-warming does not work on its own.   You can also dew heat the secondary and even the eyepieces, though putting the latter in your pocket in between uses also works.

[cpittman35]

Thank you all for the advice, links, and helpful information.  I guess I'll have to look into another red dot scope or something similar.  I have a container I can put the scope in outside a good hour or longer before I intend on using it since I'm sure the moisture can't be a good thing for the scope parts.  The "boil" visual was very obvious last night when I did have a minute to see Mars.  It looked just as you described Little Green Man. 

I can tell this new hobby of mine is going to test my patience until I figure it all out haha.  I posted this picture in another thread and I need to make sure I truly understand I won't be seeing little green men walking around the planets with my starter scope haha.  The visual I got of Mars last night was a little bit bigger than what's in the REALITY box of the attached picture but not much.  I was using a 2x Barlow and a 6mm eyepiece. 

[Dave In Vermont]

LOL! Well, then, Mr. Vacuum - now you understand.

By the by - 'Little Green Man' is the "Rank" of the member. Yours says 'Vacuum' as you're just starting out in your number of posts. After awhile you can change the automatic-rank the software generates to something you'd prefer - as I did. The top part of the lefthand of the screen says "Dave In Vermont' - and that's my member-name. Yours says 'cpittman35.'

No harm - I stand amused by these occasional faux pas!

All the best -

Dave

[cpittman35]

4 minutes ago, Dave In Vermont said:

LOL! Well, then, Mr. Vacuum - now you understand.

By the by - 'Little Green Man' is the "Rank" of the member. Yours says 'Vacuum' as you're just starting out in your number of posts. After awhile you can change the automatic-rank the software generates to something you'd prefer - as I did. The top part of the lefthand of the screen says "Dave In Vermont' - and that's my member-name. Yours says 'cpittman35.'

No harm - I stand amused by these occasional faux pas!

All the best -

Dave

LOL, I'm such a noob

That is too funny.  I honestly never noticed that.  Shows you how much I pay attention haha.   

[MarkVIIIMarc]

At some point if dew is collecting on my outside cars it might be a losing battle. Circulating air seems to help.

[cpittman35]

I had the outdoor whirlwind fan on it's highest setting pointing at the scope to no avail.  It looks like it will be semi cloudy tonight but I'm going to give it a go anyways.  I'm taking the scope out about 2 hours before use just to make sure it's well acclimated. 

[Stu]

5 hours ago, cpittman35 said:

Thank you all for the advice, links, and helpful information.  I guess I'll have to look into another red dot scope or something similar.  I have a container I can put the scope in outside a good hour or longer before I intend on using it since I'm sure the moisture can't be a good thing for the scope parts.  The "boil" visual was very obvious last night when I did have a minute to see Mars.  It looked just as you described Little Green Man. 

I can tell this new hobby of mine is going to test my patience until I figure it all out haha.  I posted this picture in another thread and I need to make sure I truly understand I won't be seeing little green men walking around the planets with my starter scope haha.  The visual I got of Mars last night was a little bit bigger than what's in the REALITY box of the attached picture but not much.  I was using a 2x Barlow and a 6mm eyepiece. 

Welcome to the world of planetary observing. They are small, or rather they are big, but far, far away! ?

Calsky may be of interest to you...

http://www.calsky.com/cs.cgi

[skywatcher58gb]

One cheat I use with eyepieces is to use 2, one in my pocket and the other on the scope, when the scope one dews up I swap them over!

[cpittman35]

16 hours ago, Stu said:

Welcome to the world of planetary observing. They are small, or rather they are big, but far, far away! ?

Calsky may be of interest to you...

http://www.calsky.com/cs.cgi

Thanks, Stu.  I created an account with calsky and will play around with it.