Forget eyepieces, I just killed my scope :( :(

[GRX40]

So I live in Montreal and there are hardly any clear nights in the winter, and its usually really cold. So tonight there wasn't a cloud in the sky but was a whopping -25(c). So I dressed appropriately and went out looking for M42.

Anyhow I noticed everything was blurry, especially in the finderscope. So I brought it in, and noticed all the mirrors are clouded. Infact, the secondary mirror wasn't even reflecting anymore.

So I let it warm up and dry inside the house and now the primary mirror is dried, and more clouded than the sky I was avoiding. And the secondary mirror has black spots on it. (possibly dirt but too scared to start fooling around with it to find out).

So guys, how much is this going to be set me back?

[mickal555]

Sounds like dew...

Was it still cloudy after warming it up?

[hhEb09'1]

What kind of scope is it?

[aurora]

Mirrors can be cleaned, but you have to be careful and do it properly. Assuming you have a newtonian and can get to the mirrors, that is. If you have a SCT or a Mak, do NOT take it apart.

There are books and web sites that give instructions for care of mirrors. check online or in your library for the Backyard Astronomers Guide, Star Ware, Nightwatch or similar book.

[GRX40]

I have an 8" Skywatcher Dob. After spending the night indoors the primary mirror doesnt seem as cloudy anymore but has numerous spots around the sides. The secondary mirror has them right in the middle however.

[redshifter]

I might try cleaning the mirrors. How long have you had this scope?

[Kelfazin]

Check this thread (http://www.bautforum.com/showthread.php?t=2564) for some good advice on cleaning the mirror on your scope.

On the mirrors, only clean them if they really really need it, as some dust won't hurt anything.

You can find instructions for cleaning mirrors in books like StarWare or Backyard Astronomer's Guide.

First, I get some surgical cotton, distilled water, and a clean spritzer bottle.

The technique is to first rinse the mirror with distilled water (spritz it down good, get the big chunks of dust off), then pour some distilled water (with no more than 1 drop of dishwashing liquid) on the mirror, and use the surgical cotton to lightly (apply no pressure, just let the weight of the cotton do the work) swirl from the center of the mirror out. Frequently turn and replace the cotton.

Finally, rinse with distilled water. Rinse thoroughly. Any water remaining can be left to dry, or can be sopped up with a corner of the surgical cotton.

I usually clean the mirror while it is still on the mount, but if you take the mirror off, a good idea would be to support the mirror in a sink with a lot of towels (to cushion it against any shock or accidently dropping it).

Finally, as to lube for the Dob's alt and az bearings, don't apply anything unless it is needed. I have used a good silicone based car wax (like turtle wax) to good affect. Usually, teflon on ebony star formica makes a good motion with no "sticktion" and won't need any extra lubrication.

[aurora]

I have an 8" Skywatcher Dob. After spending the night indoors the primary mirror doesnt seem as cloudy anymore but has numerous spots around the sides. The secondary mirror has them right in the middle however.

The cloudyness might have been dew. A primary mirror in a Dob usually doesn't dew up, but bringing it inside from the cold might have done it.

When you say "spots", what are these? Are they small, like dust? Or something else? Smudges like a fingerprint?

One thing you never want to do is shine a bright flashlight down the Dob and look at the mirror. This is because you will see dust on the mirror (no matter how careful you have been in covering it), and it will make you want to clean the mirror. Some dust is quite OK, and will have no effect on the use of the scope. Every time you clean it, there is some small chance of hurting something, so you only want to clean a mirror when it really needs it.

[GRX40]

They're little greyish smudges stuck to the mirrors that seem like they can be rubbed off with a finger or so (I won't try it, but it seems that way).

I attempted to take pictures of the primary mirror.

http://img.photobucket.com/albums/v219/GRX40/Telescope001.jpg
http://img.photobucket.com/albums/v219/GRX40/Telescope005.jpg
http://img.photobucket.com/albums/v219/GRX40/Telescope004.jpg
http://img.photobucket.com/albums/v219/GRX40/Telescope003.jpg
http://img.photobucket.com/albums/v219/GRX40/Telescope002.jpg
http://img.photobucket.com/albums/v219/GRX40/Telescope006.jpg

Around the edges of the primary, thats not dust. They look like little crusted blotches that can be wipped off with a finger and such.


Oh and they're on the secondary mirror, but not at the edges, right in the middle of it.

It's a new dob (1 month) so there isn't much dust :)

[redshifter]

It almost looks like pitting, the aluminum coating on your mirrors is pitted somehow. If that's the case, you may need to replace the secondary, I'm not sure the pits around the edge of the primary are anything to worry about, I don't think that will affect your primary's optical performance. More knowledgeable folks than I may be able to shed more light on the subject. I don't think I'd worry about cleaning the mirrors though, they look pretty good from a cleanliness aspect after looking at your photos. I've had my scope 3 yrs and just cleaned the mirrors 6 mos ago for the first time.

[aurora]

How difficult would it be to return the scope and have them take a look?

I'm guessing you bought it mail order, so the answer is, not easy.

But maybe you could call or email the company and show them one of the photos.

If it is pitting, then the mirror should be recoated. Maybe it was a bad job of coating it. Maybe they can send a replacement.

It if is something else, like maybe there was something in the air when your scope dewed up, and the gunk settled around the outside of the mirror? I'm grasping at straws here.

Hard to say from here.

[3rd Rock]

Hi GRX40, I keep my scope in my observatory/shed here in rainy cold England and every so often I get the symptoms you have described. The cure is just to wait. Honest - it gets better on it's own. I think it might be something to do with moisture in the atmosphere or something. What you say about your mirror getting a bit, but not completely, better by bringing it indoors is entirely consistent with my experiences. If you keep the scope indoors somewhere warm and dry for another 72 hours and check again, I'll bet that the mirror is back to normal. Just one final point - don't use a torch to illuminate the mirror because it exagerates any defects massively. There is not a telescope mirror in the world that looks OK when you peer down the tube when it is illuminated in this way.

Regards
Jon.

[GRX40]

It if is something else, like maybe there was something in the air when your scope dewed up, and the gunk settled around the outside of the mirror? I'm grasping at straws here.

Hard to say from here.

Thats what I was thinking. It's a relatively new scope though, would the pitting have come off that easy?


Hi GRX40, I keep my scope in my observatory/shed here in rainy cold England and every so often I get the symptoms you have described. The cure is just to wait. Honest - it gets better on it's own. I think it might be something to do with moisture in the atmosphere or something. What you say about your mirror getting a bit, but not completely, better by bringing it indoors is entirely consistent with my experiences. If you keep the scope indoors somewhere warm and dry for another 72 hours and check again, I'll bet that the mirror is back to normal. Just one final point - don't use a torch to illuminate the mirror because it exagerates any defects massively. There is not a telescope mirror in the world that looks OK when you peer down the tube when it is illuminated in this way.

Regards
Jon.

Really? Well, I'll let it be for another day or so, but its already been two and it hasn't changed. It does look like dirt, but why wouldn't dirt have collected any other day? If it doesn't go away I'll probably take Aurora's advice and try to bring it back. I don't know how I'm going to carry it in though.

[The Mangler]

Thats what I was thinking. It's a relatively new scope though, would the pitting have come off that easy?

I don't know a whole lot about mirrors and such, but as an aircraft mechanic I deal with aluminum and corrosion all the time.
Pitting will not just 'come off', it is corrosion. So if this stuff is coming off it definatly is not pitting.

[Charlie in Dayton]

I differ...those spots look to me like condensation...ya know, the famed 'waterspots on the crystal' of dishwasher detergent commercial fame.

I'd suggest trying a cleaning first. You've got nothing to lose, and if it is something more serious, at least you'll have learned how to clean a first surface mirror.

[Dave Mitsky]

I differ...those spots look to me like condensation...ya know, the famed 'waterspots on the crystal' of dishwasher detergent commercial fame.

I'd suggest trying a cleaning first. You've got nothing to lose, and if it is something more serious, at least you'll have learned how to clean a first surface mirror.

I agree about the condensation spots. They occur frequently when a cold instrument is brought into a warm (higher humidity) room.

Unless the spots create a noticeable problem, I suggest holiding off on cleaning the mirrors until it is really necessary.

Dave Mitsky

[naios]

Hi. My first post here. I have a 6" f/8 Dobsonian (I also live in Montreal). If I want to use my new telescope at all this winter I have no choice but to bring it out into the very cold air.
Bringing it inside the house, it will immediately begin fogging up and as such, I leave the dust cover off for several hours. However, this last evening I was very tired and assumed that the condensation had evaporated. This was not the case and the next morning when looking down the tube saw water stains around the perimeter of the primary mirror. I could have lived with this except that I pulled the focuser cover off and much to my chagrin saw a very water-stained secondary mirror. I realize that when leaving it to dry out that I should also leave this cover off, and that I should just leave it the entire night.
I decided to leave the primary mirror alone (will deal with it eventually) and focus on the secondary. I tried rinsing it and then wiping with an alchohol swab. That just left all sorts of streaks. After fuming for awhile my wife grabbed it and carefully cleaned with a windex wipe. It looks beautiful now however I realize that this has probably harmed the protective coating. I plan to more thoroughly read the cleaning instructions for mirrors on the internet and follow them.
I've also hear that in my situation it's best to leave the dust cover on for a few hours so that less humidity enters the tube and then later remove the cap and let it sit.
So, I can fully sympathize with the plight of grx40, but we just have to go out and enjoy the beautiful quasi-Arctic evenings regardless and do our best not to make ourselves (and our wives) crazy. I would doubt you have pitting and if you do, I would definitely contact your dealer to find out how they intend to rectify the situation (unless your telescope is very old of course).