23 replies to this topic

[Stephen S]

I am so bummed. I'm hoping someone can help me out. I recently moved cross country from San Diego, CA to Evansville, IN. It was a chaotic move on several fronts and my C8 OTA has been in storage since moving last summer. Things have finally settled down a bit so I pulled it out last week and noticed what I think is fungus on the mirror (not something I had to worry about in San Diego).

The OTA is basically new. I am so bummed. Is this the death of the scope or is there anything I can do to clean this off without significantly degrading the quality of the scope? I'll try to post pics to give everyone an idea of what I'm dealing with. I'd be happy to send this off for cleaning if that makes sense. If it's easy to do, I'm happy to tackle it myself. If it's not worth the trouble, I'll bite the bullet and buy another OTA. Any thoughts on how to best proceed would be greatly appreciated.

Thanks! Steve S.

[Stephen S]

Picture of the suspected fungus

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[Stephen S]

Second picture.

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[NewAstronomer]

Its not dead but the fungus probably eat through the coatings a bit. Needs a very good cleaning. Some say to leave it in sunlight all day before beginning to clean...I don't know if that's true but it cant hurt...of course remove corrector first

[highfnum]

i had similar problem - i took off corrector plate
cleaned mirror - used distilled water
put back corretor and realgined
pain in butt
but if you catch early there will be no damage
if you wait then it will make etch marks
make sure you mark original corrector position

[Stephen S]

OK. Thank you very much for the feedback. Sounds like a cleaning is in order. Not something I've done before so a little scary but better than the alternative.

Thanks! Steve S.

[highfnum]

how to remove corrector web sites

http://www.astronomy...aryremoval.html

http://www.ehow.com/...ctive-lens.html


http://www.astromart...?article_id=594

http://www.robertree...com/repair5.htm

[Stephen S]

Thank you very much! My next step was to try to figure out how to remove the mirror, something I've never done. You just saved me a ton of searching. Very helpful info.

Thanks! Steve S.

[ahlberto]

For removing the mirror you have to deasemble the focuser.Its a simple job to deasemble a sct but remember to mark the corrector before you remove it.Do the job on a soft place,on top of a bed or something,-if you drop something it will not brake

[Don Trinko]

If it were me I would start by not removing the mirror and see how easy it comes off. If it does not come off easy then remove the mirror. All IMO; Don T.

[OldManInHawaii]

I cleaned my first C8 mirror over 30 years ago and did so without removing it. I later sold the scope & then bought my present Meade 2080 SCT which I've kept double-wrapped in large plastic bags with lots of little desiccant pouches. My 2080 has stayed fungal-free for the past 20+ years in a very humid Hawaii climate.

[NewAstronomer]

I keep 2-3 dessicant packs in my C11 case. So far so good. Or course I keep the optics indoors in a climate controlled room (no basements!).

[Photoner]

I had fungus grow on the secondary of my original SCT Meade 2080 back in 1980. I thought the thing was ruined. Dew got inside and caused the problem.

I removed the corrector plate noting the alignment marks and taking care with the thin shims.

The fungus blew off completely with a puff of air. End of problem, used the scope for years on end.


BTW I would never use a hair dryer to blow off dew on a corrector as it might drive the moisture inward.

[rmollise]

a hairdrier isn't the best way to dry a corrector--a dew heater element is--but it won't drive moisture inward, either.

[orion61]

I have had this same problem, I don't think you have much to worry about. Absoloutly would follow Rods advice on the hair drier, but you do want to get it dry in there.
Dr Clay Sherrod has a great formula for cleaning optics, and I know of at least one company that packsges it all up for sale.
Myself I used Blue Windex filtered through 2 coffee filters
then followed by a rinse of Distilled (not bottled/drinking water)
I sat my open tube near a small sun lamp for a day and night, dried it out fine and never had a problem with it.
(Make sure it does not get too hot)
I still have the scope and it is a treasured friend to this day.
But indeed GET AT IT, every day lets the fungus eat away away....
Good luck and keep us posted

[Stephen S]

This is all incredibly helpful and encouraging. It does raise one additional question for me. The fungus is on the primary mirror. I was thinking I would need to remove the mirror from the back of the scope but that I would leave the corrector in place since it looks clean. Do you have to remove the corrector plate to remove the mirror?

Some of the feedback here seems to suggest that I should remove the corrector but leave the mirror in place. Is this correct? If I do so, it would seem like cleaning the mirror get quite a bit more difficult since the mirror is then at the bottom of the tube. My guess is I'm missing something simple here. Any addition insights before I open up the tube would be greatly appreciated.

Thanks! Steve S

[Don Trinko]

It's a little crowded but you can get in to clean the mirror.
Don T.

[orion61]

I'd remove the corrector and primary, you have to pull the corrector off. you probably won't get the rear cell off and if you do never get it back on.
when you pull the primary out you need to take the focuser off, then pull the rod back attached to the focuser, from there, there is a brass bushing that slides off a pin on the corrector cell. Sounds harder than it is. When cleaning the primary don't try to take it off of the primary holder, there is also a retaining ring on the baffle slide.
Before putting it back on you need to clean the baffle and
inside the primary slider tube.
You need to re-grease the sliding tube, don't use axil grease, TOO THICK, super lube works pretty well as does P.A.O. synthetic lube. reassemble in reverse, this will smooth the focus and should help with image shift if there is any.
good luck.

[pgrunwald]

http://www.arksky.org/asoclean.htm

[Steven]

A few cautions:

1. You need to remove the mirror+holder if you want your clean job to pass the flash light test.

2. SCT mirror may not have protected over coating. It is easily sleeked. Never wipe on it dry and only use gentle light pressure.

3. Use only detergent and water for your cleaning solution. Never get any Windex on it because it will developed pinholes.

4. Must use detergent without additive. Otherwise it will leaves a thin film of impurities (Liquinox is best but expensive).

5. Must use tissue without additives. Otherwise it will leaves a thin film of impurities (white Kleenex is best).

Steps in Cleaning:

1. After mirror+holder is removed, cleaned all the grease inside the holder with alcohol or any degreaser. Do this from the back to protect the mirror front.

2. Remove the retaining ring and the cork washer. This is done to avoid the cork washer from getting wet which will also contaminate water during cleaning. Although, the mirror is glued to the holder, from now on hold the mirror face up or 45 degree angle ONLY.

3. Use a filter on your kitchen faucet and turn it on. Adjust to room temperature and make sure it is in constant flow not jet like.

4. Prepare your cleaning solution. You will need to experiment on how strong you want it. A few drops on 500ml is a good start.

5. Place the mirror+holder face up at a 45 degree angle on the running water to remove any loose debris. Flush it completely to the right/left side of the mirror instead directly from the top which will run through the center holder (to avoid contamination). Turn off the faucet.

6. Use a few ply of tissues and completely wet it with your cleaning solution. Apply gentle light pressure on the mirror. During this time, make sure the tissues are very wet. Completely cleaning the whole surface of the mirror and constantly change tissue to avoid sleek.

7. Turn on faucet with constant flow and thoroughly flush mirror cleaned (at 45 degree angle and avoid running through center). When the mirror is cleaned, you will noticed that water will completely flow away from the surface. You will learned how to "draw" away water droplets. When done correctly, you will never touch the mirror surface to dry it.

8. Watch out for water trapped on the center between the mirror and holder. Use some dry tissue to soak it away.

9. Keep the mirror covered to avoid dust but leave some opening for air flow to dry it completely overnight.

See previous post on advice for reassembly.
Hope this helps.

Steven

[cavefrog]

ok, this may be too simple to be true. but , in stead of removing the primary to clean it, can you not remove the tube from the rear cell to have access to the primary ?

I think both meade and celestron will disasemble in this manner.

Theo

[Steven]

The issue is the rinsing method. I don't think there any home based touch rinsing method that leave no residues. Hence the total removal of the mirror and use running water to rinse.

Steven

[ahlberto]

Indeed,removing only the tube without deassembling the primary is possible..Take the corrector out and then push the primary mirror back with the focuser and you can access the srews of the tube from inside.THis is the way i clean the prymary

[Brian Risley]

First, Some of the scope tubes are glued/press fit, not screwed (older OT C-8's for example) so you may not be able to remove the tube.
Second, you need to remove the corrector on most scopes to get to the nuts on the inside if it is screwed on. If you have done that, removing the focus assembly and sliding the primary out is a lot easier to do, and you are not taking a chance on loosing squareness of the tube with the cells. This will allow you to work with the mirror out of the back, so liquids can be poured over the surface without concerns about it getting into the rear cell/focus assembly.
(Now some new C-6's appear to be screwed together by non machine screws or via threaded areas. These can be disassembled without worrying about corrector alignment. You still may want to remove the mirror once the tube is off!)
Brian