"Keep it simple" cleaning telescope mirrors 12" GSO dobsonian primary and secondary

[Tiago Ferreira]

Breaking the myth with my adventure cleaning my 12 inch newtonian reflector dob. 1st bath to this telescope. The used method is simple and effective and i saw this original way to do it by Optic wave labs and love it.

 

 

[AlexK]

Congrats for your eyesight incapable of detecting any damage so far. Let's see what you could film in a month and then after 5-th cleaning like that

Seriously. There are too many variables involved in this "method", which might work fine for some folks, but could be a disaster for others:

1. Are your hands/fingers/fingernails REALLY clean? An abrasive particle may be embedded in your skin pores unnoticeably for a long time. One can be washed out from under a too long dirty fingernail...
2. Is your tap water REALLY clean? That "shower spigot" creates quite a pressure, which could propel an abrasive flake chipped off your old rusty metal pipes 1 kilometer from your house a week ago...
3. Are you 100% sure no lose particles can be thrown from your sink sides, edges, spigot, clothes while are you working that vigorously around the optical surface which is usually handled in dedicated "clean rooms" by people in special suits?
4. If there are micro cracks in the mirror surface the sole sheer flow of water like from that showerhead could promote some of them expanding further...
5. Have you equalized the water temperature to the mirror surface temperature enough, to say that the thermal expansion/contraction haven't promoted any existing micro-cracks in the surface? Water is overwhelmingly more heat conductive compared to the air.
6. Do you know HOW your tap water is chemically treated? Many countries are still using Chlorine in their water cleaning factories, which is like an acid for aluminum coatings... So No.4:
7. Are you sure your mirror is a top grade mirror made to all optical tolerances so that its aluminum protective coating is (still) 100% intact and uniform? So the aluminum is not exposed to chlorine and other oxidizers (in the soap blob on your spigot?) anywhere through micro scratches, at the not well coated edge, through abrasions under mirror holders?

Thus: 
The only truly safe method we could generalize upon, if you are rather ignorant on most of the above is... TADA! Just leave it alone already!
Even a 10mm hole drilled in the coating is nearly nothing for most visual work. While an invisible net of micro-scratches and micro-oxidations is the contrast killer.

Edited February 13, 2021 by AlexK

[Mr Spock]

While the above post is somewhat abrupt, I'm not sure I'd want to wash my mirrors in tap water.

Given how limescale destroys my kettles and irons I'm sure it would seriously affect mirror coatings. 

[johninderby]

There is no problem using tap water and dishwashing liquid for the initial cleaning then rinsing off with distilled water afterwards. 

[Spile]

Thank you (apart from the music!) for this interesting video. I appreciate the introduction and balance you bring to this hot debate and it is welcome.

For me, the issue is a lack of evidence that a dirty mirror will affect what I will see. You use the subjective "I believe", "I suppose",, "I imagine" and "I think" throughout the video. The thing is, there is a difference between with what I think/perceive and reality. I was going to reference a certain ex-president and bleach here but I thought better of it 🙂

Until I see evidence from a laboratory that...

Cleaner mirror = Better image in my retina, my risk assessment tells me that it is safer and simpler to not not do anything.

It is not just the risk of damaging the mirror. It is about time. Cleaning might appeal to my vanity and make me feel good but without evidence that it is making a difference, why would I waste my time doing something that is not going to make a difference? Especially if I am going to repeat the exercise every few weeks or months?

This quote from the supplier of my telescope helps me:

Don’t worry, be happy

You will be surprised how much debris can accumulate without it affecting the telescope’s performance, so relax. It is all part of owning a Newtonian telescope. If you refit your telescope’s cap between observing sessions and ensure it is completely dry before storing you can go several years without cleaning.

I also read a study (I will try and find the source) that mentioned that for a 10" mirror, up to 15mm of dirt will make no difference to the image in the eye piece. 

 

Edited February 14, 2021 by Spile

[Tiago Ferreira]

This is a photo taken after this cleaning and proper collimation.

Against bad seeing and no cool down a nice dob with a cleaned mirror made the job. Love planetary nebulae:

https://stargazerslounge.com/topic/371936-ghost-of-jupiter-nebula-ngc3242-hydra-constellation

Thanks for watching and comment.

Have fun!!!

 

[Tiago Ferreira]

1 day after this cleaning (so, today)  i solved the GSO mess i show on the video with the mirror holder pads.

So i took off the primary again to put some kind of foam stickers i bought to correct that mess they had.

The new decent holder pads i put today on my clean mirror:

 

[Stu1smartcookie]

Hi everyone ... i'm sorry i am late to this party , but i am about to go back to a Dob. I have secured a 12" revelation (GSO) which i am collecting on Saturday  

Happy Days  ... The scope in question is quite old but the exterior is in very good condition , according to the photos and brief videos supplied to me. The mirrors though really do need cleaning . I am not worried about cleaning them as ive picked up many tips on how to do this from you guys on here , i am just a bit worried that even after cleaning they wont come up well. If all is lost , is there a way of getting them re-coated ? I am jumping the gun a bit here and i am hoping that they will be fine . Take a look at the photo . The scope has been stored in a garage for many years . 

Edited August 3, 2021 by Stu1smartcookie

[mert]

On 13/02/2021 at 09:30, johninderby said:

There is no problem using tap water and dishwashing liquid for the initial cleaning then rinsing off with distilled water afterwards. 

I have cleaned a few large mirrors this way, never have a problem. 

[Stardaze]

On 03/08/2021 at 13:34, Stu1smartcookie said:

Hi everyone ... i'm sorry i am late to this party , but i am about to go back to a Dob. I have secured a 12" revelation (GSO) which i am collecting on Saturday  

Happy Days  ... The scope in question is quite old but the exterior is in very good condition , according to the photos and brief videos supplied to me. The mirrors though really do need cleaning . I am not worried about cleaning them as ive picked up many tips on how to do this from you guys on here , i am just a bit worried that even after cleaning they wont come up well. If all is lost , is there a way of getting them re-coated ? I am jumping the gun a bit here and i am hoping that they will be fine . Take a look at the photo . The scope has been stored in a garage for many years . 

Orion optics recoat mirrors, details on their website. 

[Stu1smartcookie]

7 minutes ago, Stardaze said:

Orion optics recoat mirrors, details on their website. 

Brilliant , thank you ... i am jumping the gun as i believe i can clean the mirrors .. but its good to know . 

[Stardaze]

6 minutes ago, Stu1smartcookie said:

Brilliant , thank you ... i am jumping the gun as i believe i can clean the mirrors .. but its good to know . 

I bet they’ll come up just fine.