How to clean your telescope's mirrors [8" Newtonian Reflector]

[@tonypoore440]

I really appreciate how you guys show the good and the bad. Trial and error is how most of us learn a trade or skill that we will use. Please keep showing us your learning process as I know it will help many people that are just beginning or want to get into the hobby.

[@GalacticHunter]

Thank you Tony, we always make sure to include both successes and failures :)

[@andresdelaplaza]

Never put the primary mirror in the same sink that you use to wash dishes, glasses and cutlery! There will always be some greasy residues in the sink! Use a plastic recipient where you can safely put the mirror and fill it with water, so you'll be able to cover the mirror's surface.

[@figzastro-photography]

“Don’t do that or you will cry”. Lol. Good job.

[@RaysAstrophotography]

Scary, but we have to do this for the love of this hobby!!

[@survivaldude29]

I’ve only had my telescope for less than a year and it looks like somebody sneezed on the primary mirror

[@survivaldude29]

Only If there was something on the inside of A Telescope that was sticky and collected dust so Thor it would not get on the mirrors

[@scrubbingmonkeys2488]

Very good job sir. The right balance of detail and levity. As someone who was just gifted a telescope who knows nothing yet this was a huge help. Thanks

[@GodfreyTrowbridge]

Thanks for posting this. I've been worried about the 60 years of dust accumulation on my mirror, but was afraid to touch. Watched your video and successfully cleaned it today. Much easier than I thought it would be, thanks to your instruction.

[@Mrcloc]

To dry those drops, you could use a tissue that you hold about 2 inches from where you touch the drop. You only touch the drop, not the mirror. The tissue wicks the water away from the mirror.

[@donaldkasper8346]

You wouldn't just pour some isopropyl alcohol over the mirror? It will absorb the water and should dry clear. Water spots? If you used distilled water, why does it matter if spots remain? There won't be any residue from the drying of the drops.

[@leatherindian]

Wetting the lint free towel and wringing out the water works to get the spots off. This is one of the best cleaning videos I’ve seen. I suspect we’ve watched many of the same to learn the process. This is worth a subscription. Thanks!

[@CafeBikeGirl]

A hair dryer is what is typically used for when cleaning super soft samples for metallography and should be very safe to use on a telescope mirror, safer than using a microfiber towel. Just make sure you tilt the mirror and blow all the water downward so that all the impurities collect in one spot and get blown off the edge.

[@chip6954]

Al Nagler changed my perspective on cleaning optics/mirrors decades ago: glass cleaner - paper towel - done! I remove the mirror assy (indexed to the tube), leave the mirror assy intact, blow off any loose stuff, spray glass cleaner on the exposed section of the mirror, wipe off with microfiber towel (no lint), put the assy back in, re-collimate, and done. No issues/degradation, no opening Pandora's box with disassembling everything, no mess, no wasted water, takes 5 mins; done it 1-2x a year for last 25+ years on my Dobs with no change other than switching over to microfiber towels.

[@benryder8190]

thank you for the easy to follow step-by-step guide. it took a lot of the worries out of cleaning my mirror for the first time

[@tomeks666]

I did it for the first time yesterday. My procedure was simplified. I washed primary without detaching it from the cell (my cell has no electric fan). Also I did not use destiled water nor towel. I just washed it with water with some dish fluid and rinsed it with tap water until no drops were left. Remaining very small drops I blew away with a compressed air dust cleaner. No smallest scratch. Looks like factory new.

[@astrodad656]

I like this approach. Plan to try it this weekend. Thanks!

[@donaldkasper8346]

@@astrodad656 I think your mounting bracket screws are not stainless and will rust.

[@maxverstappennonofficial]

​@@donaldkasper8346 I guess if you dry them well quickly I don't think so.

[@donaldkasper8346]

@@maxverstappennonofficial They will rust from moisture in the air unless coated or stainless.

[@jeanrenaudsagswing]

I own a crappy scope with a spherical mirror on f/5 ratio. I plan to replace it with a parabolic one. So for fun i cleaned the old one. Not much care, i used my fingers (not pushing too hard) and even had to scrape off residues that were not leaving, using my fingernails. I dried the mirror by putting a towel on the surface gently. Pretty sure no one should follow my method :) I think there is a scratch somewhere but cannot prove it was me that did it with my fingernails. I will replace it anyway. There is less dust than before.

[@brianvalente]

Thanks for the tip on not tightening the primary down too much - just saved me a lot of grief

[@Eddie42023]

When I do this (never less than 7 years, more like 15, between cleaning the same mirror), I use cotton balls (I can get cotton pads in various shapes as well) and hold them such that they absorb the water drops from the surface of the mirror without even making contact.

[@Green_House]

Suggest marking mirror cell and tube before disassemble so they also go back the same way. Tube and cell screw holes will then align correctly.

[@kenn7915]

Well done and good job; but, I want the unedited version where we can hear the frustration and rage etc. 😀

[@GalacticHunter]

Hahahaa there would be too many "beeeep" sound effects

[@ToddChevrier]

@@GalacticHunter LOL...Been there...done that....but it is for the love of this hobby! I found the frustration more in collimating than cleaning.

[@gregorymckenna6609]

Excellent and informative video. I might suggest a nylon screwdriver when working near a mirror as it is less likely to cause damage if it slips.

[@BackyardObservatory]

I made that mistake once, just once.

[@GalacticHunter]

Thank you and great tip!

[@donaldkasper8346]

You hold the screwdriver with two hands. One to turn, the other to hold the tip on the mounting bracket. Then it cannot slip.

[@caelib8229]

This video was incredibly helpful, I was able to follow your steps exactly and successfully clean my mirrors! Thanks!

[@Omni8Canada]

Do you need to completely remove the primary mirror from its housing to wash it?

[@blackred8]

Your video helped me out so much. I found a reflector telescope thrown out by a school. The mirrors were still good just dirty.

[@Jarlaxleify]

Great video, I really appreciate you helping us learn from your mistakes and challenges! I had ash from a campfire 20 meters away land in my telescope, so I had to clean it and you helped a ton. Thank you!

[@TheWonkyAstronomer]

I know the stress. I've cleaned my 12-inch mirror twice in ten years. Great video.

[@starhopper457]

You did fine!! Don't forget there is a layer of SiO2 coating on the top. That provides a level of safety/security so you can use the towel as gently as you did. Well done! (I clean my mirrors and corrector plates all the time.)

[@silencedogood7922]

Oh, and I love your videos. Thanks for letting us learn through your experiences and trials and errors. I've learned a lot scrolling through your catalog of videos. Keep them coming!

[@GarnettLeary]

Did you come across my cleaning video in your KZbin travels? I’ve got a great one on pinched optics too. If I were to offer advice I’d suggest lining your sink with a rubber mat. Mirrors can be slippery. It’s much more forgiving had you dropped it. You can mix rubbing alcohol with the distilled so that you’re not left with water spots. You can bypass touching a drying mirror that way. Additionally it’s important that people know that the majority of newtonian reflectors arrive with the mirror clips overtightened. That’s done so that there’s less chance of it breaking during shipping. I’ve never seen that referenced in any telescope manual.

[@GalacticHunter]

Hey Garnett, I don't think I saw your cleaning video but I just checked my history and I did come across your Pinched Optics video! Thank you for the help!

[@GarnettLeary]

Galactic Hunter any candidates for the APOD? Have you decided on a target yet?

[@GalacticHunter]

@@GarnettLeary Yes but we've had a lot of equipment issues recently, we want to make sure we take care of those before attempting a difficult target.

[@GarnettLeary]

Galactic Hunter Awesome. You’ll get it. Your edits look good. It’s just a matter of time. I still believe it will be with the Newtonian. Clear skies.

[@Cusnpbzn]

isopropyl alcohol for final rinse?

[@gilgarcia5719]

Thank you very much, I couldn't find the answer why the stars look triangular in my telescope, until I saw your video. Thanks again.

[@Tim_the_Astronurd]

I bought this scope in July, thanks to you guys and have love love loved it! Now I need to clean mine so Im back here for a refresh. I think I can do it. although every time I look into the primary mirror and see my reflection I now say "Oh hai!" lol, thanks Antone

[@GalacticHunter]

Haha glad to hear, good luck! Make sure to only do this if and only if it looks really bad, not worth the trouble if there isn't that much dust on it :)

[@tihomiryosifov9804]

Hello, to stay out of troubles I remove first secondary with the whole spider, clean, put back and colimate Then remove primary clean, put back and colimate. If the secondary got out of colimation, I put a sheet with concentric circles at the place of the primary and align with a colimator. Also I use the cotton to clean the mirror under water. Then use blower to get rid of the drops

[@sammypembo]

Do not attempt after drinking or with a hangover!!! And never... never use a impact driver to unscrew everything!! 😂🤣 Great video and some quality tips mate 👍🏻👍🏻👍🏻

[@BackyardObservatory]

Like the video. Sadly, I had to abandon my Newt as the mirrors glaze over every few months where I live. For drying, might I suggest low lint, or lint free, paper towels. You tear them into strips and can get a very fine point which sucks up water droplets almost instantly.

[@stew_redman]

I work with medical instrumentation. We never use paper towels on glass lenses or mirrors as they are actually abrasive. If you have to dab or wipe then lint-free cloth is the way to go, especially micro-fibre lens cloths.

[@BackyardObservatory]

@@stew_redman I've tried microfiber lens cloths and found the absorption rate was way to slow for larger mirrors, or a significantly larger contact area was required. With the strips I'm suggesting, it only needs a couple fibers to come in contact with the droplet.

[@astrojourneyuk]

I saw another tip which was to put a clean tea towel in the water in the sink to protect the mirror and the sink when cleaning that seems a good idea.

[@twisterwiper]

Very nice video. I was particularly interested in knowing how the mirror assembly was constructed and how the mounting and collimation screws act on the mirror assembly. Thanks 👍🏻

[@JuanCarlosBustamanteBrauer]

Great video, straight to the point and everything explained, thanks!

[@tchallalemou5307]

Any laser calibration issues with that specific collimator?

[@ugphysicsspc5056]

Beautiful informative video. We have 8 inch reflecting telescope cleaned the primary and secondary mirror as given in instructions and assembled. Now ready to watch great conjection of two giant planets. Thanks for video.

[@Mikem-mq2hh]

"be careful not to smash your screwdriver into ze mirror, or you will cry..." Excellently put!

[@derbezacesanchez3779]

Will canned air work as a first step before the distilled water.

[@gammondog]

Squeeze bulb would be safer. I tried canned air and tilted it, causing liquid air to strike the mirror in the center. It made a mark. Fortunately it was only on the center.

[@Snail2G]

Followed the exact instructions step by step using quality cleaning products and my mirror is covered in scratches now 🤷🏻‍♂️ not sure where I went wrong (don't think I did) but, yea. Time to shop for a 6" mirror I guess

[@dragonseps8058]

Good summary of "how to" 's out there! Thank you 🙂

[@koalaboygaming346]

A thing that helped me was getting a secondhand telescope that I don’t really care about if I damage it so I can try out cleaning that mirror before I actually clean my main telescope mirror.

[@DawidKellerman]

Hi you are only suppose to use the cotton wool once not turning over look at Willie Koots 's channel

[@patrickdonnelly5223]

Use water flow to remove and not cotton? Even cold plasma might be safer?

[@jimmosley3382]

Great video thanks for sharing how to do this.

[@hcic9860]

Would using a can of Compressed air help in not having to take it apart at all?

[@srikanthyadake]

Thanks for these tips. Cleaned my 5 inch primary mirror 😅

[@dannybray2443]

Hey I have the cheaper version of the reflector my primary mirror does not have a center mark. Can I add my Own on it? own if I bandage it out right

[@TheKokomploko]

If we make a mark with marker in mirror where you do it we do not make a problem to mirror?

[@podcarste613]

Hi! I don't have those back screws in my rear mirror... I have a skywatcher 150mm... How can I make collimation? Anyone can help me ?

[@ExoPhotography1]

Nice guys! I made a video just a couple of weeks ago how I am cleaning my mirror... I think the hardest part is not the cleaning itself, but as you slightly mension, the drying-up part. I did pour destilled water over my mirror afterwards and it came out almost spotless from water residue.

[@GalacticHunter]

Yes! The drying-up part was pretty annoying, especially for the primary mirror.

[@derekderek2570]

I cleaned my primary mirror with windex and a rag and it came out perfect. The most important thing is the positioning of the corrector plate the glass is pretty resilient. Also this is a very used $400 Orion scope, not a Takahashi Mewlon-300 CRS, you can relax lol.

[@LTECharged]

I did it with some rubbing alcohol and some toilet papet

[@chip6954]

The lengths people go to and actually stress over this simple task is amazing to me 😬😄

[@Dobviews]

Thank you! You just saved me so many hours!

[@MrAwol007]

Great video buddy just a quick question my sct corrector plate cracked and there is small bits of glass in the main cell what would be the best way to remove the glass without harming the primary cell thanks.

[@ManishFrenchStudio]

Superb video ❤️❤️❤️ lovely, thank you for sharing ❤️🎉🎉🎉

[@AstroDenny]

I use denatured alcohol and a large microfiber sensor wipes. Works great.

[@maurizioangelo64]

Hello Galactic Hunter, i made this risky work for two times in 6 month in my Newton F4 telescopy, the humid and not clean air outsider in the nights go inside telescopy during the large nights of sessions. I made ever more fast that work, but with more risk of damaging the miror. The method that you use is the best and saffety. Ever the problem is the collimation after... But this is annother history.. hahaha. God job!

[@GalacticHunter]

Thank you Angelo! Yes we were really annoyed when we realized we had a couple of issues on the next night and had to disassemble the whole thing again ☠️

[@maurizioangelo64]

@@GalacticHunter noooo, for the collimation? I one month ago have two weeks,(yes two weeks) traying to collimate well, is very hard for fast Newtown telescopy. I read and learn a lot of threads. The problem was that also I need to fix the ocular collimation and not only primary and secondary mirror. But in the end the positive results was done!

[@nicksastrophotography330]

Next time, mark the primary mirror holder and the tube too. Then you will not rotate the mirror when you put it back. I have a newt with a corrector plate in front. I wouldn't want to rotate one or the other. Maybe it's less of a problem if you don't have the corrector plate. Anyway, nice video again 👍

[@GalacticHunter]

Thanks Nick, I didn't mark the tube because I knew I just had to rotate it until the little fan in the back was straight, but if I didn't have that fan there that would definitely have been good a good thing to do!

[@rase4341]

Thank you very much, this is very very useful!!

[@garcia9352]

esa foto del al principio del video con grupo de galaxias la isiste ? tu con el niwton 150 y a q grupo pertenece ?

[@mariusflorea1984]

"be careful not to smash your screwdriver into your mirror.... or you will cry" that was epic xD xD xD

[@Boekoe12]

video on how to clean filters would be awesome!

[@stocksj]

Would using canned air help in cleaning off the dust?

[@galenburns69]

Thanks for sharing great video really helped

[@TheflickerofMotion]

Well done taking it on yourself Antoine, not that bad after you have done it once, and yeah your primary mirror was pretty dusty. Great video for anyone brave enough to take it on...you included plenty of advice.

[@fighterjetdude990]

How warm or hot should the water be

[@pranjyotidas4290]

What is the screwdriver no.?

[@gunderstrmberg3501]

Thanks for a very informative video. I am just done cleaning mirrors on my SW Explorer 250pds while closely watching this video. Are You sure that the clamps to hold the primary mirror should be that loose? There was some slack when I dismantled it, but not as much as you show with the business card. I have had problems with the telescope holding colimation before taking it out, but have not yet had the chance to see if it now is ok. Gunder

[@cmas-astronomy4715]

Great video. I have found that if I only wash it with water and a little dish washing soap, that there is a haze left on the mirror. I use another washing step with 91% ISO & soap and then a final rinse with distilled water.

[@fishsquishguy1833]

I’d only use Dawn dish detergent. Some of the others have moisturizing stuff added for your hands but they could leave an oily residue.

[@richardcampbell2261]

I have to do this for mine as the my images are looking like yours. Soon I will need to get a new scope. I am looking for an intermediate one.

[@gunnarjensen5910]

I pulled the primary mirror from my 12 inch do and tried to clean it. No luck. Seems mat or oxidised. Can I use a metal polish to make it shine again or do I have to get it to an expert to re-coat it ??

[@jantomik6885]

what if you wash the primary like a whole holding cell you will avoid possible issues like triangulum shaped stars or bad colimation holding, or its a bad idea to drop a whole holding cell with a primary to cleaning bath? 😁

[@jimawhitaker]

I don't even own a telescope I just wondered how this is done. I felt tense watching this ;-)

[@daviddenson3324]

And you had to recollimate too correct?

[@andyweeks2216]

I think I made the pinched optics mistake that I'll have to fix! Thanks for the tip!

[@GalacticHunter]

Good luck!

[@bootheethaikhtun3901]

Me too.

[@bootheethaikhtun3901]

@@GalacticHunter Thanks for the videos.

[@Beaver-be8vk]

Air duster or a paper towel corner works best for drying the mirror.

[@williamlane2213]

I have the XT10. I can't see what size tool or type is needed for the collimation screws on the secondary mirror. Please tell me what you used. Thanks

[@GalacticHunter]

I just use a laser collimator which goes in where the eyepiece normally goes: bit.ly/2NqAUcy

[@kinshuksinghania4289]

Could we use a spray?? Shouldn’t we use distilled water in the final wash and let the last drops evaporate?? Coz distilled water has no dissolved substances and it should not leave any water marks when the water drops dry out!! There would be no need to wipe the last drops dry!! Just saying

[@xtrithx4389]

I'm having to do this for the first time because I bought a lens pen from celestron and it did more harm than good. It smudge and even SCRATCHED my mirror. I've never been soooo pissed off because there was a flaw in the design were the tip of the pen was made of rubber and smudged and Scratched my mirror because it would flip the tip on its side while cleaning.

[@stevenholt824]

Hi.. I would advise only using bottled or distilled water for washing as tap water can contain fine suspended particles of grit that will scratch the mirror when you rub it with cotton wool. UK.

[@GalacticHunter]

Oh I had no idea, thanks for the tip!

[@fernandoluna2025]

I have a dumb question... So my dobsonian Orion XT6 has been an awesome telescope for more than 14 years, so me being the idiot that I am, decided it needed some maintenance and ended up removing the "spider" that holds the second mirror ... And now I don't know it it's correctly centered!!!! Help... How do I know if I messed everyone up or how do I re center it...

[@PuneetBanga26Aug]

Hi, I am from India , recently i have bought Orion xt8 Classic Dobsonian. Couple of days back while using telescope , my 25 mm plossl eyepiece botton metal part accidentally hit primary mirror and small black coat inside of metal part of eyepiece stick to primary mirror. By 25mm eyepiece while watching moon , it look good. But using barlow 2X n 25mm eyepiece to see Jupiter on full zoom , not sure but i think that black coat scratch on primary mirror is shown in eyepiece. Please let me know, What to do: Does it really effect on light gathering. Do i need to clean it , if yes please tell me simple way, as i am first time user. Or it wouldn't effect the view.

[@materialdialectics]

Thank for this video, I've got an 8" newt too. Although personally I find most of the time if it is just a case of getting dust off the mirror I just rinse it off with isopropyl alcohol--granted that's a tough thing to find at the moment. Rinses the dust off, dries fast and doesn't leave behind any residue most of the time. Of course sometimes just giving is a rinse isn't enough, around where I usually set up there's always dirt bikers kicking up dust on the gravel roads that inevitably finds its way on my primary mirror. Sigh.

[@GalacticHunter]

Oh that's annoying.. When we were filming the review for that scope, we were on a dry lake and there was a bunch of people in dirt bikes and quads riding around, that was pretty scary for the mirrors.

[@mikebenengtouncry3613]

I remember this from a couple weeks ago !! great job :D

[@GalacticHunter]

Haha yes on Instagram 😂

[@greglight5808]

Very educational video! Love it keep up the great work

[@GalacticHunter]

Thanks Greg!

[@jasonr4082]

I watched same video you watched 😂 still didn't feel confident but you vid helped a lot! Thanks man got yourself a new suscriber

[@Cien_Swiatla]

Can I use a different marker instead of the sharpie?

[@GalacticHunter]

Yes it doesn't matter, just don't touch the mirror

[@Cien_Swiatla]

@@GalacticHunter OK, THX :-)

[@Cien_Swiatla]

@@GalacticHunter what do you think about blowing off the water droplets with compressed air?

[@searchproduction9658]

Can use odicolon cleaning telascope mirror sir. Please tell me

[@MrBercis]

Definitely no! Perfumes contains oils!

[@ashedite2962]

Te agradezco mucho! Hace bastante que mi telescopio esta sucio y siempre tuve miedo de lavarlo, por el temor que me generaba saber que podría dañarlo. Mañana me tomare mi tiempo y seré lo mas delicado posible para lavar los espejos!!

[@astroandreacolucci]

Thx dude! Today my dobby got its first bath after almost 2 years.

[@alexanderkbt]

Wie kann ich das Dreieck vermeiden?

[@running2standstill685]

Im a beginner and was forced to collimate my telescope because it was not focusing propely on stars and also due to my idiocy. I was only using a collimating cap with no donut in the mirror, took me 3 hours and i was stressed as hell. I shudder at thought of eventually doing this as well. That being my collimation turned up okay as i am now able to focus on stars properly with those 4 beautiful spike radiating from the stars.

[@mystic_spore4752]

There’s like a couple little dust particles on my primary mirror and when trying to photograph the sky you could see them blurred in the photo and only photos

[@taylorjammin]

Not trolling, but why would tiny scratch ruin images?

[@highspeedboom]

I clean my all my primary and secondary’ with distilled water from a brand new garden hand pump garden sprayer, use cotton balls if the spray doesn’t remove the dust. And dry with empty garden sprayer pumped up with clean air. I almost never have to touch the mirror surface. Drying the mirror with compressed air using good quality distilled water will not leave any residues behind, just a perfect clean mirror. I also never remove the primary from the mount ring support.

[@maurizioangelo64]

Hello, yes it is possibile if is only dust, but the air near the City and industries where I live is dirty and this durty with dust go inside the telescopy and stick it over surface of miror. This is impossibile to take of if not use some soap and warm water.

[@GalacticHunter]

Interesting, I had no idea it was possible to clean the mirrors this way!

[@highspeedboom]

@@GalacticHunter , I have found out over many years that the less you have to touch the mirror the better, and I don’t use soap and cotton balls unless needed. The gentle water spray, and gentle air for drying is usually enough. I have restored many telescopes over the last 40 years, and no touch technique is the best. I have used a small amount of isopropyl alcohol added to the distilled water, if the primary had mold growing on it’s surface to help kill it and prevent it returning. A high humidity storage area is to be avoided.

[@alalal1979]

@@highspeedboom GREAT info! I have finger prints on my mirror.... You think this could work for them? Thanks to you and thanks @Galactic Hunter for the great video

[@highspeedboom]

@ hmmmmm , Fingerprints usually only come off with distilled water , cotton balls with mild soap, then rinse with distilled water. Dry with air or dry cotton balls.

[@RaymondCHowes]

So I might ask a silly question. But that's the only way I find out things. Since you took off the whole primary mount, do those little nuts inside stay in place on most telescopes? A few weeks ago I bought my first inexpensive scope. Celestron 127EQ. It's nice for the price. But the more I learn. The more I see the little issues with it. It seems like a problem for me if I remove the whole mount and those little nuts fall out. I'd rather skip the frustration by asking silly questions.

[@Tim_the_Astronurd]

did your center dot stay on? Im not sure what to do about it as I dont have any extra. Im just gonna cross my fingers and go for it as I have a rare night this friday to image and I gotta get that thing cleaned off!

[@jeffreyyoung4104]

Get a box of paper reinforcements from the local office supply. The plastic ones work best for a mirror dot. And you will have enough left over to do everyone else's telescopes!

[@Tim_the_Astronurd]

@@jeffreyyoung4104 luckily mine did not come off! but good idea

[@nicklewis7240]

I had pinched stars and couldn't figure out why. Thank you, it was the screws too tight. All the stars were triangular at 10mm, was frustrating.

[@charimuvilla8693]

Since people use hairdryers without damaging the mirror I wonder if just blowing the dust away with one is sufficient without any water.

[@brianhusk4593]

Thanks for the video. I'm guessing you can't just windex the mirrors? lol. Also, I wonder if a lower psi air compressor would be ok to use to help dry?

[@8688nick]

What happens if I got my greasy fingers on it...Will this method work? Thanks 😞