Cleaning Celestron corrector plate

[maltrabob]

Hi all,

I need to disassemble the optical tube as I need to clean the corrector from both sides to get rid of fungus. I would appreciate your advice regarding a cleaning fluid for this job. Celestron recommends using a blend of isopropyl alcohol and distilled water. Since I have no pure alcohol nor isopropyl one and have no time to order as I want to start cleaning tomorrow, is it safe to use Baader's "Optical Wonder" fluid instead?

Here's what I plan to do:

1.) get rid of dust and dirt using Celestron LensPen brush

2.) spray a bit of Optical Wonder on a Kleenex non-scented tissue and gently wipe the corrector plate.

If there's any lint coming off tissues I will use Baader's "Scratch Free Cloth" that came with the fluid (but I would rather not to as I am not sure if I already used it before or not and want to avoid the risk of scratching the plate).

Here are some pictures I took today:

Celestron cleaning guide: http://www.celestron.com/support/knowledgebase/articles/how-do-i-clean-my-telescope-optics-%E2%80%93-primary-mirrors,-lenses,-eyepieces,-corrector-plates

 

Thank you.

 

[LukeSkywatcher]

The wonder fluid is designed for glass rather then coated mirrors, so that should be fine to use with a lint free cloth. Instead of a lens pen, i'd use a "rocket blower" firstly to shift anything that may cause a scratch. Even dragging a lens pen across the glass could cause the debris to scratch it. I wouldnt use any kind of kleenex or unscented wipe either as they may still leave a residue on the glass. 

Please dont take my word on anything. Wait for a few more replies before doing anything. Are you sure it is a fungus and that it is on both sides of the plate?. Doesnt look like fungus to me.

[maltrabob]

Hi Paul, thank you for your reply. I am pretty sure it is fungi that grows on a corrector plate from inside. It is hard to capture on camera, but it looks like it is spreading and creating moist around it, see my updated first post. Kleenex was recommended by Celestron themselves as well as some professional who tested it against a dedicated optics cleaning wipes, but I will use it with caution as I also found a post that wasn't too keen on using Kleenex. Rocket blower's been added to my wishlist, thanks for mentioning it.

 

//forgot to ask, what does it look like to you then Paul? That "fungus" thing I mean (those definitely aren't some kind of micro cracks or similar, I double checked).

[opticalpath]

Are you quite sure that it's not just condensation on the inside surface of the corrector?  I did get that once and it looked odd.  Cured by placing some silica gel in a bag in the eyepiece drawtube an leaving it for a couple of days.

If you're sure it is something else on the corrector lens that needs cleaning, the way I found best for cleaning the outside surface was as follows (and which could probably be used for the inside surface after removal). 

NB.  This is NOT a method to be used on mirrors!

- Position the OTA horizontally, so the corrector lens is vertical.
- Blow off any surface dust with a blower brush (or canned air with great care to avoid spraying the propellant)
- Buy two cheap plastic spray bottles; clean thoroughly and put some distilled water in one and 100% IPA in the other. Keep them clean in a sealed plastic bag
- Make an absorbent pad with towelling/ tissues and place at the lower lip of the top of the OTA where it will absorb run off
- Spray the bottom half of the corrector (from central boss to lip) with neat IPA so it covers the lower 50% and runs off into the towelling pad
- Immediately repeat using only distilled water
- Blow off excess with a blower brush and inspect
- Repeat two or three times as necessary, changing absorbent pad as required
- Flip the scope over so the corrector is again vertical, but this time with the other half of the corrector on the lower side
- Repeat the process on the second (lower) half of the corrector

If it looks reasonably clean after that, stop now - you cleaned it without touching!

If there are stubborn stains remaining that you feel the need to tackle, I have used unscented Kleenex mens tissues, but with no pressure.  Make a soft wad and soak it 50-50 distilled water and IPA. Without applying any pressure, move this wet swab across the stain once; turn it over to a fresh surface and swab again, always with no pressure on the corrector. Don't be tempted to wipe back and forth with the same piece of wetted tissue, or to apply pressure. If the stain resists, try neat IPA.  If it still resists, I would not persist.

If you end up with some drying streaks on the surface, either ignore them or try a final spray/ rinse with distilled water with a VERY small drop of baby shampoo or washing up liquid added. Not everyone will agree with this, citing the salt that these products contain to thicken them.  I can only say that I have never had a problem using a very weak solution like this.

Adrian

[maltrabob]

Thanks Adrian for your tips. I am planning to get a desiccant cap for my C9.25 to prevent problems I have with this C8. Your way of cleaning a corrector plate sounds good, I will give it a go tomorrow (got 5 litres of de-ionised water from Halfords to keep me going :)). Having no IPA though, I will stick to that Optical Wonder thingie and post my results here when finished.

[LukeSkywatcher]

From the first image you posted, it looks to me like something had dripped onto the plate and hardened (cant tell for sure). It does look like (due to slight shadows cast) that it is perhaps only on the outside surface of the plate?.

I know what you mean about the moist ring around it. This in my mind says it is some kind of bacterial growth?. Not sure if thats even possible on a glass plate without feeding it as in a petrie dish.

The blobs on your plate look well encrusted on and to be honest i am not sure of the best approach. When you find out what they are and how to remove them....clean the remaining dust off with the wonder fluid and lint free cloth.

[LukeSkywatcher]

How is the view through the scope?. Do you notice the "blobs" when observing?.

[maltrabob]

The view through the scope is pretty good, here are my single shots of the Moon from some time ago: https://stargazerslounge.com/topic/106395-my-first-moon-shots/#comment-1050578 Would be much better with tracking and stacking hundreds of frames and also with some dew prevention. So from this point of view I think it was okay and I haven't noticed any annoying defects.

I will open it tomorrow and give that corrector plate a good clean, can't wait :).

 

 

[maltrabob]

I had a go today and I took things a bit further than I planned first - I cleaned a primary mirror as well :). Now just need to clean a secondary one and put it all together. Here are some picts from today.

A bit concerned about a secondary mirror to a corrector plate position as I forgot to mark it. Will see if that was a big mistake or nothing to worry about when collimating the scope later (I did mark a corrector plate vs tube position though).

 

[LukeSkywatcher]

I was gonna suggest that you mark things before taking them apart. Not sure how simple it is to put it back in the right position. Best of luck.

[Stargazer33]

I believe there is normally an orientation mark on the secondary. Not sure where it is or in what position it sits. I will try and find the article where I read it and post a link.

[Dave In Vermont]

Dr. Clay Sherrod, an expert in all-things-SCT, has an advanced guide to cleaning the optics on these scopes. Here's the link:

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

Good luck,

Dave