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New Climate, new ways to prevent dew/condensation

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#1 Stacyjo1962

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Posted 03 June 2020 - 10:25 PM

So, being from Northern California for all of my observing since I first got started in this wonderful hobby, I never encountered the intense humidity of Houston area (I am not including the area of Northern Alabama I grew up in...didn't have equipment back then)...

 

How does one prevent dew, condensation on optics and mirrors?  My equipment gets stored inside when not using and I have experience in letting the optics come up to ambient temperature in my previous area(s) of observing, but now...wow!  Humidity is nuts and it's only June LOL  lol.gif 

 

Would like to learn the tricks of the trade in fighting dew and condensation in my new, adopted area - for as cheap as possible...not a whole lot o'cash right now for new, ancillary equipment...

 

What I've got:

 

50mm refractor - thinking one of my cotton or silk scarves draped over the optics while it's coming up to ambient temp will do the trick

80mm refractor with dew shield - same as 50mm - but the StellarVue will get the Hermes silk scarf

6" table top dob - no clue

12" Orion dob - haven't hooked up electronics for auto star hopping and doubt I'll will - I like to star hop manually  - really no clue!

 

I have a multi-temperature hair dryer and a really good general usage fan - would these be useful?

 

Thanks all for any and all help!!!

 

Clearest of skies...St.

 

 


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#2 ascii

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Posted 04 June 2020 - 05:43 AM

I live in Florida, so I have the same problem.  I just have refractors.  I just leave all of the caps on my scopes and eyepieces when I set them outside to warm up.  This traps the dry air-conditioned air in the spaces near the glass surfaces.  (I either cap or have an eyepiece inserted into the diagonal.)  Once everything thoroughly warms up, I remove the caps.  If it is particularly humid, I may have to towel off the exterior surfaces of the scope.



#3 havasman

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Posted 04 June 2020 - 06:29 AM

Active dew control works and is, where I observe, simply required. For the larger Dob you're probably going to need a heater for the secondary. Astrosystems dew control products for secondary mirrors are excellent and have sophisticated sensor/controllers built in. For eyepieces, finders and refractor objectives I like the controllers and strips from R-Sky a lot and their prices are lower than some more famous suppliers. The tabletop Dob may only need airflow from your fan to remain clear.

 

But in the mean time your hair dryer may be a lifesaver. Not too hot though.

 

Welcome to Texas! Houston is a fine town and has good highways that run all the way out to West Texas where the sky is darker and the air is usually a lot drier.


Edited by havasman, 04 June 2020 - 06:59 AM.

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#4 spereira

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Posted 04 June 2020 - 06:59 AM

Moving to Equipment, for a better fit.

 

smp


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#5 HouseBuilder328

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Posted 04 June 2020 - 07:31 AM

I am wondering about the same thing.  NC now has tropical-level humidity!   I bought an AstroZap dew shield for 9.25 SCTs and am going to try that. 

 

I think I'll put the scope in the garage first for a few hours, before observing.  Think that will help?    Inside the A/C is running non-stop with the thermostat set at 78 degrees.  Afternoon outside time is 92 and in the evening probably around 82. 

 

https://www.highpoin...evolution-az132



#6 vsteblina

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Posted 04 June 2020 - 04:43 PM

I would move back to northern California.....what were you thinking??

 

It is a shock to deal with dew. 

 

I live on the edge of the "Great Columbia Desert" in eastern Washington. The Federal Reclamation Department got rid of the desert after the building of Grand Coulee Dam.  But, except in winter, it has had minor impact on the climate.

 

I bought a mountain home 28 minutes from Wenatchee on a high mountain meadow. I still remember that first night at the property wondering "what is this?".  DEW????

 

And then it dawned on me...a Forester for 30 years at that point....a mountain meadow means DEW!!!  Ok, I had a office job at that point for almost 20 years.

 

My solution was wait....dew is an issue until the meadow dries out in July.  I even went out and bought a Kendrick set-up but it wasn't worth the time it took to  run cables and wires to everything..

 

DEW, it is a major issue for astronomy.  Fortunately for me, DEW is an issue during spring when we have only a couple hours of darkness.  

 

I gave up and just observed at my "desert" home during DEW months.

 

IF moving back is NOT an option. 

 

I really was impressed with the Kendrick system.  BUT it was easier to go observe at my light polluted home for a couple of months until the meadow dried out.


Edited by vsteblina, 04 June 2020 - 04:44 PM.

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#7 SonnyE

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Posted 04 June 2020 - 05:13 PM

Dew occurs. (My dog sez, doo occurs. But that's a different kind of thang.)

Solutions vary. But heat strips are the best option I know of.

The trouble there is the horrendous price they want for what they are.

So me being me, I scratched up some surplus resistors I had, did a little measuring, and made my own dew heater.

I was doing star trails at the time, and needed my DSLR set up and running all night.

I could cover everything but the lens with a gallon bag with a corner trimmed out.

But the problem was the dew on the lens. So my home-made series of resistors, inside Velcro, wrapped around my lens put enough heat into the lens to keep it dry.

I just hooked it up and let the gentle heat keep the lens ever so slightly warm.

 

My Telescope has a dew shield on it (ED80T CF) and I've never suffered dewing on it's lens.

But I think that has a lot to do with Location, Location, Location. I'm close to the edge of the Mojave Desert here. So fairly dew free.

(But my yard isn't. So I police it everyday for doo drops. Usually in the afternoon, so they've had time to harden a bit.)

 

But if you have a dew problem, maybe the best thing would be to save up and get a dew system. <that's a link<

Here's a good place to start looking, and thinking.

 

And not to worry, I did do my dooty already today. It's been hot, so the drops petrify really quick.

Picking up Dog doo is a lot like picking up women. It gets easier after they've aged a bit. wink.gif lol.gif


Edited by SonnyE, 04 June 2020 - 05:18 PM.

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#8 Pedalpoint

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Posted 05 June 2020 - 12:46 AM

You didn't say whether you were transporting the scopes or using them at home. When I'm transporting they're in the back of the pickup and no problems with them being at ambient.  Nowadays, though,  I've been doing the driveway thing in this COVID world which means that setting the scopes out at dusk to let them warm up if they've been in the air conditioning.  I set mine out on the screen porch--an open garage door is useful, too, if you keep them in there.

 

You know those nice holes they put in tripod spreader bars to put your eyepieces in?  Never use them--they're worse than useless in a humid environment.  You'll have a bunch of dewed-over eyepieces if you use those holes!  And keep the lid closed on your eyepiece box, or you'll be sorry.  I've toyed with the idea of putting a Kendrick heater in my eyepiece box.

 

I've been observing in the driveway, and I've found that a pedestal fan and an extension cord to be a very useful thing. Helps the scopes stay acclimated and has the side benefit of confusing the mosquitoes! Go downwind to apply mosquito spray since DEET eats optical coatings.

 

Your refractors shouldn't be much trouble, really.  Refractors do well in dewy environments.  But the dobs will have issues.  Not so much with the primary once it's warmed up, but the secondary dewing over as the night goes on.  That's a real hassle and can be hard to solve. You have to use a light shroud on a trusstube dob, for sure.

 

Charts and books need to be covered or something when you are not actively looking at them.  I keep a towel on top of mine to keep the dew off. Oh, and it's just great to sit on a dewed-up observing chair! Another towel.

 

There are not many good solutions for dew, just coping strategies!


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#9 HouseBuilder328

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Posted 06 June 2020 - 07:15 AM

You didn't say whether you were transporting the scopes or using them at home. When I'm transporting they're in the back of the pickup and no problems with them being at ambient.  Nowadays, though,  I've been doing the driveway thing in this COVID world which means that setting the scopes out at dusk to let them warm up if they've been in the air conditioning.  I set mine out on the screen porch--an open garage door is useful, too, if you keep them in there.

 

You know those nice holes they put in tripod spreader bars to put your eyepieces in?  Never use them--they're worse than useless in a humid environment.  You'll have a bunch of dewed-over eyepieces if you use those holes!  And keep the lid closed on your eyepiece box, or you'll be sorry.  I've toyed with the idea of putting a Kendrick heater in my eyepiece box.

 

I've been observing in the driveway, and I've found that a pedestal fan and an extension cord to be a very useful thing. Helps the scopes stay acclimated and has the side benefit of confusing the mosquitoes! Go downwind to apply mosquito spray since DEET eats optical coatings.

 

Your refractors shouldn't be much trouble, really.  Refractors do well in dewy environments.  But the dobs will have issues.  Not so much with the primary once it's warmed up, but the secondary dewing over as the night goes on.  That's a real hassle and can be hard to solve. You have to use a light shroud on a trusstube dob, for sure.

 

Charts and books need to be covered or something when you are not actively looking at them.  I keep a towel on top of mine to keep the dew off. Oh, and it's just great to sit on a dewed-up observing chair! Another towel.

 

There are not many good solutions for dew, just coping strategies!

 

When you put them in the open garage or front porch, do you leave the caps on the front and eyepieces?  What about a cover over the telescope while it's warming up?
 



#10 Pedalpoint

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Posted 06 June 2020 - 07:10 PM

It just depends on the temperature. When bringing scopes out from cold a/c to humid/hot outside, I leave the caps/covers on to keep the optics as dry as I can, letting them warm up gradually.  Once they've been outside for a while, then I'll open them up. The goal is to keep the optics dry.  I just use my glasses as an indicator--if they want to fog up when I go outside, then the scopes will and I'll have to do what I can to keep the optics dry. It's usually not a big deal here in TN, although when it's REALLY hot and humid is when you'll have to take precautions. I used to live in Florida and it was horrible there, with the dew falling before the sun went down!

 

In the winter I do the opposite, opening them up quickly so as to start the cooldown process. 


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#11 Napp

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Posted 06 June 2020 - 07:44 PM

I’m in Florida so dew is almost always bad.  The nighttime air temperature tends to track very close to the dew point.  Refractors and SCT’s need dew shields and dew heaters.  I also put dew heaters on the finder and the eyepiece.  The warm humidity of the eye can cause condensation on the eyepiece.  Actually I’ll wrap the dew heater around the diagonal so I can exchange eyepieces easily.  You may need a dew heater for your DOB secondary.  A hair dryer can be used instead to deal with condensation when it starts to form.  Always point the hair dryer across the glass and not directly at it.  Do not use the hot setting.  I keep a 12 volt hair dryer with me because most of my observing is at remote sites.  I always leave the cooling fan(s) on for a DOB.  When dew is really bad it is possible for condensation to form on the primary mirror.  Running the fan(s) helps prevent condensation.  There are dew heaters available for primary mirrors.  I have not gone to that extreme, however, I have encountered a few nights when the dew was so bad that all my measures just were not enough.  You may or may not need to use all the methods I covered based on your local conditions.

 

As important if not more so than dew control is what to do with your equipment after a session.  Most of my observing is at remote sites so I put everything back in its cases for transport.  I will wipe excessive moisture off the mount and tubes of scopes but certainly not optical surfaces.  However, when I get home I lay all my equipment out uncapped and uncased under ac/heat until thoroughly dry.  I lay scopes and eyepieces on their sides to prevent dust accumulation.  When everything is completely dry I cap and case everything. 
 

Welcome to humidity and high dew points!


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#12 whizbang

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Posted 09 June 2020 - 06:17 PM

Napp nailed it.  I deal with dew exactly the same here in Seattle.

 

And, like pedal point conjectured, I also have dew heater strips in my eyepiece case.  I keep those babies toasty.


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#13 Stacyjo1962

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Posted 23 June 2020 - 03:02 PM

Thank you all...since I have both refractors and reflectors, and being at home for the moment, I'm going to attempt the gentle fan technique...when it clears up LOL...been having some incredible thunderstorms of late!

 

I'll most likely be experimenting with various avenues and will post as I can on this topic...doing my "dew" diligence and "dewty" to all CN'ers (H/T to SonnyE) 

 

Yes, I was very, very spoiled in Northern California! lol.gif




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