How to Clean a Reflector Telescope Primary Mirror - Complete Guide

Hey everyone!
In this video, I dismantle and clean a used Sky-Watcher 250 1200/F4.8 BKP 250 OTAW-dual speed Newtonian Reflector telescope. This telescope was sitting in a garage for a long time and got dusty.
Lucky for us here at Jelispace, buying a used Sky-Watcher Reflector helped us keep our Astronomy/Astrophotography hobby relatively affordable.
In this video, we show you step-by-step how to clean the primary mirror of your reflector telescope.
* This process should be done as needed and will keep your telescope performing at its very best!

[@BoNERul]

Very clear and concise instructions; one of the best out there. Thank you for the time and effort.

[@JeliSpace]

I appreciate that!!

[@nicotower9354]

great video -- extremely helpful. Thank you!!

[@JeliSpace]

Glad it helped!

[@nathanhaber1513]

Good one 👍

[@JeliSpace]

Thank you! Cheers!

[@lavers_1]

thx for the vid!. how often do you need to clean it?

[@JeliSpace]

Not very often really only worth the risk as needed. Just make sure to keep the dust cap on and if possible you can store it with the mirror up so that any dust that is in the tube wont settle on the prime mirror. They one I got in the video was used and stored in a barn for a few years so it was very dusty!

[@JeliSpace]

Did you have one to clean? Or planning on doing it soon?

[@kevincarter7102]

If you could scratch the Mirror by pushing too hard on a cotton ball, shouldn't we be wearing nitrile gloves. That way you don't possibly scratch the mirror with something like, oh I don't know, a fingernail?

[@JeliSpace]

That is a great call out!

[@jasonwall5012]

27:50 mine is different at the end. It has 3 hex bolts inside and 3 Phillips heads. It hasn't got the round circle crisscross thing. Also, I'm very appreciative of your mirror clean, I just looked into mine, and it needs a clean, and the tube might need a wipe. 1 question: Was the water cold or warm or hot. Big up from Dublin, Ireland 👍🏼😊

[@JeliSpace]

Water was room temp for this. Hope that helps! Good luck!

[@ROY-COLLEY]

Hi Glad I found your Vid..I have just started to take out my mirror on my skywatcher 250pds. I'm also going to flock the inside tube. Have you flocked yours ? I've also put Bob's Nobs on secondary mirror makes it easier to turn Collimation.

[@JeliSpace]

It is interesting that you mention it, I have not flocked it, however I had an idea to try that vanta black paint in the tube. Which might work better? Not sure if you have seen it before but its pretty interesting. However its not high on the list of projects.

[@rwoodin3]

Great video that provides some vital tips. I would not have known about the business card as feeler gauge step! I'm taking my Meade 10" SCT off the pier and putting my SkyWatcher Quattro 250P back on. I want to clean the mirror before doing that. I just bought a GSO 2" Barlow lens that I'm hoping I can get focus with, for continuing to image galaxies, at a longer focal length with greater magnification, while they're in season! I found that the 250P reflector focuses on stars and DSO's soooo much sharper than the SCT it's no contest. Autofocus on SCT gives best focus star size between 7 and 10. The 250P reflector gets stars autofocused to between 2 and 5. Thanks again for the great info!

[@JeliSpace]

Thanks for the kind comment Goodluck with galaxy season I know I will be getting ready for that after the eclipse 😊

[@SterremanWillie]

Nice video, although I'm always worried to scratch the mirror with any dust or particulate matter stuck on it. I thus start off by first rinsing it under a running tap to get rid of loose dirt. One's fingers are amazingly sensitive and can detect things down to a few microns, so I then make sure all particulate matter is gone by gently wiping it with my fingers, still under running water. After that, I'll go over to the soap-stage. I use very little soap and a final rinse with copious amounts of distilled water. I use cotton wool to wipe it dry. See the two most viewed videos on my channel.

[@JeliSpace]

Haha, it sounds like you've got quite the mirror-cleaning routine! Who knew fingers could be so sensitive to dust? Keep those mirrors sparkling!

[@AI_Karen]

Then on your way back to your telescope you trip over the cat.

[@JeliSpace]

LOL yeah that thought did cross my mind!!

[@josmty9]

Thank you very much for this video, it’s exactly what I needed, I have same telescope, only it’s 6”, I had it at storage for 2 years and now I want to use it I notice that mirror has lot of dust…. I’ll follow your instructions. 😊

[@JeliSpace]

Hey I am glad it helped! Just remember get everything setup and ready before you begin and you will be done in no time!

[@AstroPixUK]

Great tips. I’m super tuning my 800mm f4 in the summer, while I flock the tube, i thought I’d give the primary a clean.

[@JeliSpace]

Hey cheers! Hope the video helped. I gave you a sub enjoyed the daytime polar align video! Actually plan on making a similar video soon seeing as I live right in the line of the upcoming eclipse!

[@AstroPixUK]

@@JeliSpace thx and good luck :)

[@stephenmarcinko812]

Anyone ever tr a drop of like a rain ex clear mixed concentrated

[@JeliSpace]

We considered using Rain-X concentrate, but it may leave streaks on the mirror. Cleaning manually allows you to inspect it as well.

[@johnmorrell]

Can you tell me why you loosened the secondary, and then didn't realign it, after you tightened it? Didnt it move out of position?

[@JeliSpace]

After disassembling and cleaning the telescope, we typically collimate it and tighten everything during reassembly.

[@dtalbot34]

Why not small bursts of compressed air to remove excess droplets?

[@JeliSpace]

That thought had crossed my mind. I the reason for the excessive care is the coating is bare aluminum, and it is so very very thin. Basically when they are making the mirror the vaporize the aluminum and the vapor settles onto the glass. That is about it! so maybe a blow dryer or something more gentle but I am ok with just using a paper towel maybe next time I will try something like that.

[@johnmorrell]

Compressed air often has oil propellant in it, so you can inadvertently spray oil on your mirror by mistake. I never use it as I can't be 100% sure there's no propellant in the can.

[@mladenpuzigaca381]

Thank You a lot!

[@JeliSpace]

You're very welcome. Thanks for the feedback

[@gregerianne3880]

Nice video! Thanks so much. I've had my 6" Dob for a couple of years and it looks like the mirror is due for a cleaning, but I was nervous about taking it out and cleaning it. Your video eased my fears a bit. 😃 I wonder if it's overkill, but after I adjust my primary mirror with a laser, I go back and check the secondary again and do a couple of iterations. Thanks so much again! Very helpful.

[@JeliSpace]

Hey I'm glad to hear the video helped. I say why not honestly once you get everything setup and all tools at hand a few checks won't take long at all. Good luck!

[@gregerianne3880]

@@JeliSpace I cleaned the mirror today! It was so easy I kept thinking I forgot something. 😀 Thanks again!

[@JeliSpace]

@@gregerianne3880 that's awesome glad the video inspired you to do it!

[@balamena]

This method is not good. Use First contact Polymer. A little expensive but your telescope will be more than brand new.😊

[@JeliSpace]

Thanks for the tip. I will have to try this out. I will point out the method I used worked perfectly fine for me but results may vary.

[@aa.6976]

just clean the thing...what a joke //its a mirror..thats it,,,,its not a scientific surgical procedure,lol...funny man

[@JeliSpace]

Well its a little more complicated than that. Mirrors we use for checking our appearance have the reflective materials on the back of the glass making them very robust to cleaning. However with a reflector telescope it is a very fine coating of aluminum on the surface, it is very easy to damage it. So yeah a little extra care is called for in this case.