Telescope Use

[moosemanuk]

Hello all,

Hope you don't mind me starting a new topic for this, but couldn't find my answer anywhere else, and hopefully some discussion might come out of it!

I recently got an 8" Dobsonian after years of using a 4.5" Equatorially mounted scope. The images I get are spectacular, but I am sure they could be improved! One major problem I have is eyepieces frosting up or gathering condensation when I am outside. I leave my scope outside with the eyepieces for a couple of hours before going out on a sub zero night but the eyepieces and the finder (but not the main mirror) are either frosted over or have condensation on them making images extremely blurry.

Does anyone have any advice for how to keep the eyepieces free from moisture while out observing? Or the finderscope for that matter?

Thanks in advance!
Clear skies (not too many here in England at the moment!)
Moo$e

[Bluewolf027]

You could try the Kendrick dew remover system from what I have heard they work well and they aren't too pricey.

Astro-Physics Inc Sells the products
http://www.astro-physics.com/index.htm?pro...rick/dewremover (http://www.astro-physics.com/index.htm?products/accessories/kendrick/dewremover)

Im sure there is many others around the web as well.

[TheAstronomer]

Hey, Guy...

There's a couple of very simple tricks that will help reduce the problem you're having.

First off, you're doing the right thing by allowing your eyepieces to come to outdoor temperature before using them. To help keep errant moisture away from your eyepieces, add a few silica packets to your eyepiece case. These common little packets are often found in many types of packaging, and they absolutely eliminate the odd moisture that collects simply from use.

Now, rather than go to the expense of looking at an eyepiece heater? Think about what you're doing that causes the frost. You got it... Your breath. While observing in the ultra-low temperatures, try tying a bandana around your mouth and nose, ala "outlaw" style. A simple painter's mask or filter works equally well! When in a pinch, if you wear a scarf, it will work too, but the thickness of the material often gathers the moisture and makes it uncomfortable to wear.

Just a couple of simple tricks from a longstanding observer...

Rockin' the Night,

~T

[fleetwizard]

Hey Moose,

Cover 'em up! ;)

Personally, I keep mine in their plastic holder, which sets in my carrying case until I am ready to use them. I have the outside of the holder marked with the size of the EP that is in it. I also have those sitting in my carrying case with the lid down, but not locked.

If I am switching between a couple of EP's regularly in a session, I will keep the one I am not using in a pocket in my observing vest.

As far as the finderscope, I gave that up when I discovered Telrad, but you have the same problem with it. I keep a small piece of cloth, similar to a handkerchief with me and when the condensation starts forming, I cover it with the cloth til I need it.

Hope that helps some.

Oh, and you're not alone with the lack of clear skies! :wacko: :rolleyes:

[Daniel T]

I use the Kendrick Dew Remover. It works great, if you don't mind the extra stuff: Wiring and power supply. I have heating elements on everything except the eyepiece. On my 8" SCT I've put heaters on the corrector plate, finder, and Telrad. ( Yes I have a finder and Telrad both. I need all the help I can get! ) Interestingly enough, I've never had a frost or dew problem with the eyepiece. Maybe that's because I change them so often. Before I had the heaters I just put a small towel over the finders until I needed them. That worked fine.

Speaking of frost, I've had my dobsonian out on some really cold nights and the entire telescope ends up covered with frost! The mirror doesn't appear to be effected, but I'm a little concerned that all that ice may not be good for the telescope in general. I keep it in the garage and the ice is gone the next day. Anyone have any thoughts on that? Should the end cap be put on after use? My main concern is the mirror.

[TheAstronomer]

Hey, Guy...

I keep the majority of my scopes in an unheated garage as well. Don't worry. The Celestron has seen 15 years of service and shows no problems with the mirror save that of use. The 12.5 mirror is more carefully guarded, but stored in the same way and also shows absolutely no ill effects after over a decade of use. (actually, the coating is in far better shape than many scopes i have seen that were "younger" and less used!)

Just be discrimating about what conditions you take your dob out in... That's why I also have many other "workhorse" scopes. When the scope stays well covered, it's safe from dust. If it's off the floor, it's safe from moisture. If you feel like the conditions warrant it? Try turning on a fan in the garage to circulate the air, but take care to cover the end of the scope with non-linting, breathable material, like linen. (i do this in the summer when it's very humid.)

Other than that? Enjoy it!! If you get condensation marks on the mirror, you can eventually clean it. The best scopes are the ones that are used...

Rock on,

~T

[dmccabes]

I keep my scope outside on the porch here in Mass, but I keep my eye pieces inside. The moisture/frost forms with warm moist air on a cold surface. The warmer the eyepiece, the less this will happen. Eye moisture alone can cause this problem. During very cold nights, I fold down the eye guard and keep my unused eyepieces warming up in my pocket. The 35mm PanOptic is a real challenge :D
Breathing out the side of my mouth helps. I also discovered holding your breath is not a good idea since you very rapidly loose night vision, and the background sky begins to turn rather gray. Good luck and lets hope we get an early spring!

[TheAstronomer]

Hahahahhaaaa!!

I liked your anecdote about breathing! I know I've caught myself more than once holding my breath - like I'm in anticipation of something - and not even realizing it. Don't cha' love those little swimmie things that happen in your eyes when you do that?

All the best,

~T

[Blondin]

I also recommend the EP in the pocket trick. I have a Kendrick set up but I just found it was more trouble to keep wrapping and unwrapping the heater every time I swapped EP's so now I just swap the EP's between my focuser and my pocket when they start to mist up.

[TheAstronomer]

Hmmmmm... I do sometimes put my eyepieces (in their cases) in my pockets, but never really thought about doing that to keep them warm. Just as often, I leave them in my case kept near the scope.

I do keep my eyepiece cases under the same conditions as I do my scopes and have never noticed a particular problem unless I breath on them. Usually, it's not an issue unless it is blazing cold. The major problem comes during the summer when an eyepiece is kept in an air conditioned environment and then moved outdoors into humid conditions.

It may just be me, but I seem to have the best luck just keeping everything at ambient temperature.

Rockin' the Night,

~T

[Jet3050]

You can also lower the amount of Condensation that collects on the eyepiece by keeping them high up off the ground. Such as the Eyepiece Rack on the Orion Xt10, the rack is too low to the ground where condensation collects easy. I have had this problem many times and find that if I keep them higher from the ground they will stay clear longer. But if your finderscope on your telescope is also fogged up then it is inevitable that the eyepiece will condensate also if this is your only defence tactic alone.

-Kyle