How to Remove and Clean an SCT Telescope Corrector Plate - FRONT AND BACK

[@Astronurd]

Thanks for that Vlad 👍 This will give a lot of folk the confidence to clean their own Cassegrain telescopes

[@AVTAstro]

I hope it does!

[@jeramiescott3364]

What a find. Stored mine corrector side down for a good while and oil leaked on back on plate. Thanks for this tutorial.

[@AVTAstro]

Hope you get it nice and clean👍

[@eltorrisimo]

Thank you for this. Would like to see you remove the mirror cell. Unfortunately my mirror cell spins when I try to remove the fastar ring. Do you know if the secondary mirror cell is supposed to go in a particular orientation, similar to the corrector plate? Some seem to think so. Nice video.

[@AVTAstro]

I have not seen any definite evidence that there is a perticular orientation for the secondary. In regards to removing it, some are quite tough. I would apply some heat(heat gun) to the thread area. In a lot of cases this is all you need to get the threads loose.

[@eltorrisimo]

@@AVTAstro thank you!

[@THICKSPICK]

Thank u Vlad for this. In your opinion is this a good time to do collimation ? Also how would you do a Refractor or Binos?

[@AVTAstro]

Well I check for collimation almost every time I use my SCT. But especially if you did pull the corrector I would check it. I'll probably eventually make a video of cleaning a refractory objective but its really the same exact procedure as the corrector plate.

[@permafrost7781]

Nice video thanks Vlad. I will be cleaning the secondary with the Televue recommended cleaning mix and cotton instead of windex and lens cleaning towels going forward. Quick question, I bought my CPC 1100 from a previous owner who was also using a hyperstar. I realized my middle secondary turns from on top from where it writes Fastar and where the 3 collimation screws are. My corrector does not move though. Do you think that's a problem? My optics are great though. Concentric rings are great when out and infocusing on stars. Starizona sells a 15$ gasket ring that one can buy and install. I'm just chicken to get it done though lol. Ever done this or heard of this before?

[@AVTAstro]

Yes i certainly would never put windex on my of my optics. As far as the secondary ae long as the scope is producing an image you are satisfied with i would not worry about it. I have never done the gasket kit, but it it just involves removing the secondary such as when you would install the hyperstar its VERY easy.

[@monkeybones671]

Hey AVT! Thanks for the video. I recently transported my CPC 1100 in a pelican case. Once I got to my destination, I tried to collimate and I have so many issues. The secondary retaining ring vibrated loose during transport and lifted out of the notch (this was the beginning of my problems). I fixed this and now cant even get close to collimation. The scope will not focus but when I get close, I get a really weird comet coma (kind of looks like a badmitten ball). I am almost positive that the corrector plate vibrated and rotated during transport. I checked the corrector plate ring screws and they werent snug. I was able to tighten them a little but didnt move all of them because I was scared of messing something up. I would love to hear your feedback and any help/suggestions you could provide.

[@AVTAstro]

Hey, sorry to hear about the issue. Sounds like it was a really bumpy ride! In regards to the corrector rotating I would not worry too much about that. I really don't see a force that was applied to it from the bumps in the road to rotate it significantly. As far as the collimation, you are just really far out of whack. I have seen exactly what you're describing in the diffraction pattern. I can almost 100% sure you that nothing is wrong with the scope. You will just need to adjust the secondary more then normal to get from the Comet patern back to the donuts. How? Try loosing one screw(significantly) and see if you get back to a good patern. If it's not that screw then tighten it back up and try a diffrent one. Again losen, and not tighten for this procedure.

[@monkeybones671]

Thank you so much for the response and advice!! Im so frustrated because any adjustments I have made don’t seem to move it back in focus at all. I will definitely try what you are talking about. Its my last resort before sending in to Celestron which I definitely dont want to do. Ill let you know if this works.

[@monkeybones671]

I forgot to ask about the corrector screws. Are they supposed to be snug or tight? The ones that I tested were fairly loose.

[@AVTAstro]

So when your initially trying to get back to the doughnut pattern have them pretty lose. Once you set the collimation they should be very tight. That's what will make it stay collimated.

[@siegfriednoet]

Very interesting video, well explained ! But what happens if the corrector plate is not in the same position, so rotated ?

[@AVTAstro]

Well the scope will still work. It will not produce an image that's as sharp though.

[@mrh9635]

@@AVTAstro Could you manage to find the optimal position yourself if sending it back to the factory wasn't an option? I may be faced with that when my replacement comes.

[@decibellone696]

I know this is old. but i inhearted a Meade SCT and had to clean EVERYTHING... so i think i did a good job but i found on reassembly a bit of dust on the inside of the corrector plate. - is this a concern or can i just move forward?

[@AVTAstro]

Do not worry about the dust. That is nothing that will affect the final image👍

[@jwbcsb822]

Please provide a link for the blower bulb that you are using in this video. I understand there are many models I'm interested in yours specifically.

[@AVTAstro]

I bought it years ago in a camera store. I highly doubt that it's still made.

[@amsetus]

Great Video. Just got a Celestron C8 that has been negelected for at least 20 years, it was kept without the rear dust cap, so there is plenty of dust and mold on its interior. I have seen in your video that you mention not to manipulate either primary or secondary mirrors. I'm strugling to either try to clean it from the interior with a long brush or disasemble the back part of the telescope. Any suggestions? Thanks.

[@AVTAstro]

To properly clean the primary mirror you would need to take apart the entire OTA. This is very involved. You can try to clean it off as best you can with the mirror still in the scope but will likely put some light coating damage on the mirror unfortunately.

[@sembrandocielos2022]

@@AVTAstro Hello Vlad! TIA for this content. I am just at the same point as amsetus. Got a Celestron 8" and primary has quite a lot of mold. So by removing the primary and cleaning it properly would the coating be safe still? Second question, the actual process to clean the primary would be by sumerging it and then destiled water, right? Thanks a lot.

[@ziggyfrnds]

Thanks for this Vlad! I just bought a +20 year old C8 for very cheap, kind of like a barn find. The OTA is in good shape, no dents or anything but the corrector plate looks quite dirty so i'm going to try this. The focuser looks ok, I could only test it in daylight and looked at some faraway trees........the image looked ok, not blurry but with all the dirt on the corrector plate not v good either. From the outside the primary looks fine and i'm not going to touch it as per your advice. Any other tips to restore an old C8? Thanks again!

[@AVTAstro]

Congrats on the new scope! Yeah just clean the corrector first. I dont see any other things that you would need to do.

[@ziggyfrnds]

@@AVTAstro Thanks. Just waiting for the weather to clear up here in water-logged sydney australia :-)

[@ziggyfrnds]

@@AVTAstro Thanks for taking the time to reply! actually the image was degraded because the prism in the diagonal was dirty, i've cleaned that up will check image again. I took out the corrector plate and cleaned it like in your video but it still looks weird. Its got discoloration.....plus the previous owner probably tried to clean it themselves too because the cork (or plastic) which holds the corrector in place is gone and the corrector is kind of loose in its housing.

[@ziggyfrnds]

If possible can I send you an image of the corrector plate can you please guide me how to clean it (or if I should leave it alone). Would like some expert opinion on it :-)

[@AVTAstro]

Yes just shoot me an email with it: [e-mail]

[@jackfrost4033]

I had to remove and replace 4 screws in the primary housing to replace the red dot finder and install the starsense undoing the screws was easy, putting them back in was more difficult especially towards the end with significant forcing is this abnormal?

[@AVTAstro]

Really should not be difficult at all. Make sure they are not too long as they can run into the primary mirror.

[@bussi7859]

I use a mixture of 9 parts ether and 1 pare pure gasoline, on the end of a stick I roll a ball of pure cotton, dip this cotton ball once only in the mixture, sweep it in a spiral from the centrum to outwards. Behind the sweep it must be absolutely clean. Continue with freshly wetted cotton’s until the optic is cleaned. Do it in ventilated area. Use strong light. The mixture works in a way that the ether dryes instantaneous and the gasoline lubricates. Don’t contaminate your mixture with your fingers or a second dip with a used ball. I do this with all optics from amateur Teleskop to LASER optics. Everything that stains for a longer time like fingerprints it gets burned in for keeps. Do not use water, dry cleaning, blowing and don’t rub. Store your ether safely it is really dangerous and if you store it for a long period it can react with oxygen into an explosive. Buy only small amounts of it and after the use get rid of it.

[@AVTAstro]

Sounds interesting but I feel like this method should have a "do not try this at home" warning for most people.

[@somebodysnobody9113]

Thanks for posting this! I just picked up a ALMOST new Meade 8” 203 emc, I know.. it’s old but amazing optics. The corrector plate did have some stuff on it . Don’t have to clean it yet but took some of my hesitation away from doing it eventually.

[@AVTAstro]

Glad I could help!

[@BenHouston3D]

Thank you! I did this process this evening and it worked great.

[@AVTAstro]

Glad to hear that it worked out for you👍

[@pjaro77]

I dissassemblied the front glass cover and figured the corrector lense needs to clean too. But it is located deep in the black tube. So i buyed printhead foam swabs long stick from aliepress. And I dont use the the cotton wool to clean the glass plate anymore. Special cloth from optic store which dont release the hairs is much better.

[@AVTAstro]

Sounds like your talking about the primary mirror. There is not really a good way to clean it without pulling it out of the scope.

[@pjaro77]

@@AVTAstro I mean the lense corrector in the middle of primary glued inside long tube with the primary together. I dont know how it happended but the corrector was pretty dirty.

[@pjaro77]

@@AVTAstro Why do you think the primary should be disassembled out of the scope if you want to clean it ? The main tube is quite wide, you can place the hand to the mirror easily.

[@AVTAstro]

Cleaning a mirror is nothing like cleaning glass optics. The coatings are VERY easy to scratch(and you will scratch them unless it's out of the scope). You need to remove it and have it submerged in water just like cleaning a dob mirror.

[@pjaro77]

@@AVTAstro OK, but i dont want to disassembly whole telescope for cleaning.

[@MikeStAmand]

Thank you for this. Perfect timing for me.

[@AVTAstro]

Glad it was helpful!

[@avt_astro206]

Great Tutorial Vlad!! Hope you can Make one of how We Can Remove Dew from a Secondary mirror of Newtonian. Thanks for sharing! Clear Skies

[@AVTAstro]

Thanks! So are you talking about how to cleaning the secondary mirror on a dob?

[@Astronurd]

Buy a secondary mirror heater or use a dew shield to prevent it. Once there, use a hair dryer

[@AVTAstro]

If talking about dew removal I'm with Ian 100%!

[@GT_09_Actual]

Thank you so much!

[@AVTAstro]

Glad it helped!

[@HollomanUFOLanding]

Very helpful video, thanks.

[@AVTAstro]

Glad to help👍

[@elincognito8509]

Al final si se puede sacar los hongos del telescopio?

[@AVTAstro]

Yes all the mold clear off!

[@christopheguigot841]

Excellent 👌 France 🇫🇷 nickel..!!!

[@AVTAstro]

Thabks for the support 👍

[@Michael.Chapman]

The ‘flashlight test’ you performed at the beginning will make even a new scope look dirty. Celestron mention this in their documentation. Mould is the enemy of all optical coatings…

[@AVTAstro]

That's not really true. You just need to know what you looking for. Celestron puts that in the manual to not have 100's of calls a day from people likely buying thier first scope.

[@Michael.Chapman]

@@AVTAstro on thinking more about this, and viewing a range of cleaner and dirty SCTs on YT, I agree with you. A matter of experience and discernment :-)

[@hael8680]

What is in the cleaning solution?

[@AVTAstro]

It's 60% alcohol 40% distilled water with a diny drop of Dawn no fragrance/dye dsh soap.

[@hael8680]

@@AVTAstro Thank you!

[@netmaster78]

Any chance you do a video on removing the primary mirror?

[@AVTAstro]

I could do that in the future, but currently don't have any SCT's that need this done. If I may ask, why are you removing the primary?

[@hael8680]

Wouldn't Kimwipes be better than cotton balls??

[@AVTAstro]

I have heard of people using them with good success. Never tried them.

[@ConnorRoss]

the corrector plate actually just came off, the bond seemed to have disintegrated in the sun/rain

[@AVTAstro]

Glad you got it off. Was it stuck?

[@mrh9635]

I attempted this a few hours ago on my C9.25. I removed the secondary first before pulling out the corrector plate, though. I suspect this may be part of the reason a hideous crack developed reaching out from the centre about 10 minutes after I reassembled it. A quick google search seems to suggest the plate cannot simply be replaced. I'm in deep s**t. If you think you know why it cracked I'd suggest you update this tutorial. For anyone else reading this don't believe these astro-pundits when they tell you not to be timid or afraid of removing the plate. Be afraid. Be very afraid.

[@AVTAstro]

Wow, sorry to hear that that happened. I have pulled over 10 corrector with no issues. I have not ever even heard of this happening before. Its a pretty thick piece of glass. There really is not stress on the glass by doing the procedure. If I had to guess you may have already had some kind of stress fracture on it before pulling it.

[@AVTAstro]

BTW send me some pictures of what's going on. I want to see this for myself: [e-mail]

[@mrh9635]

@@AVTAstro Okay, thanks. As I was putting the screws back in one gave me a bit of trouble. Somehow it didn't seem lined up with one of the 'gasket' things and I struggled, perhaps applying a little too much pressure to get it home. Other than that, I'm clueless.

[@AVTAstro]

Yeah that must have been what did it. The corrector was probobly not quite sitted all the way back in and tightening the screw put enough pressure to fracture it. Bummer to see that happen:(

[@mrh9635]

@@AVTAstro My fault. I had no reason to remove it other than to see how simple it could be done. That Ed Ting said in one of his videos, 'it's not a question of ''if'', but ''when'' , something like this happens--if you spend a lot of time around scopes'.

[@parkershaw8529]

That is a FAT cat!

[@AVTAstro]

😆 🤣

[@charlesburks3988]

😢 scratch scratch scratch scratch. Over time. The best way is not the easiest

[@AVTAstro]

Not sure what you're saying? What is the best way?

[@charlesburks3988]

@AVTAstro my opinion. Mark orientation of corrector. The corrector needs to come off secondary off. Treat like you would a priority mirror. Some would say that's too much. It is definitely a bigger job. Every time anything comes in contact with any optical components, a chance of scratches/sleeks can happen. Over time, it can add up possibility damaging in the long run. It's very hard not to leave residue unless rinsed with distilled water, in place that can not be done. It's kind of a pain, but to chase the best possible views it's better. My personal opinion. Clear sky happy hunting.

[@schwarzerkuerbis]

Don´t be this guy. NEVER hold the corrector plate mid-air instead of putting it safely down somewhere. Be intelligent!

[@AVTAstro]

Lol, yes I'm not very intelligent. Don't be me and hold the corrector for like 30 sec to the a picture. The world will stop spinning.... lol. Sorry could not resist.