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Posted (edited)

I've owned optics for decades and have cleaned front elements many times, but never, until now, a mirror.

A year or so ago I bought off @neil phillips his 300p Newtonian, and I must say I think it's a rather good mirror. He mentioned when I took it off him that "it holds collimation very well" and he was right. I've had three consecutive observing sessions, full removal from and attachment to mount each time, when I've not needed to adjust anything, using a Cheshire collimator.

It lives here in SW Ireland, and I'd resolved after a year to at least inspect the primary and see if it looked as though it needed a clean. There's been a bit of work done on the house here, bringing mucho dust, and there are also lots of spiders. Needless to say, once I'd removed it, there was evidence of much spider-action! I have no prior experience of whether mirrors need cleaning or not, but I judged this one was just the right side of spider-webbed and dusty that it could do with one?

A couple of rinses in detergent-water and eventual careful application of cotton-wipes rendered it more or less pristine. The final image below still shows a couple of stubborn spider-silk threads, but I let those go. It'll be interesting to see how it "views" when the clouds clear next...

Magnus

 

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Edited by Captain Magenta
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I used to clean my old Charles Frank mirror once a month for years and never had a problem with any damage so not sure why people are so afraid of doing so....

Alan

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Posted (edited)

Yes I think the aluminium is coated with SiO2 these days so quite tough and impervious to the care we generally take to avoid scratching.

Edited by Captain Magenta
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3 minutes ago, Captain Magenta said:

 quite tough and impervious

 

I do think that cleaning telescope mirrors sometimes being regarded with fear is unnecessary, perhaps being “ quite tough and impervious “ a bit overstating it, if you don’t mind me saying so 😐 although you did mention to avoid scratching.

But if you proceed with due care then it’s a routine job that need not be a worry.   And I’ve seen some really grotty mirrors that still gave a good view, so no need to rush to clean unless contaminated with salt air or tree pollen etc.

Definitely no offence meant......but just in case a newbie reads and gets out the Brillo pad........😀

Ed.

 

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4 hours ago, Captain Magenta said:

It'll be interesting to see how it "views" when the clouds clear next...

Hiya Magnus. Looks like you've done a nice job on the cleaning. If possible, let us know whether you noticed an improvement or not :thumbright: 

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On 23/08/2019 at 00:42, Rob Sellent said:

Hiya Magnus. Looks like you've done a nice job on the cleaning. If possible, let us know whether you noticed an improvement or not :thumbright: 

... needless to say the dust I’ve liberated immediately set to work seeding clouds!

as soon as there’s clear sky I’ll report back...

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Looks like it came up nicely :thumbsup:

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On 22/08/2019 at 22:15, Alien 13 said:

I used to clean my old Charles Frank mirror once a month for years and never had a problem with any damage so not sure why people are so afraid of doing so....

Alan

Turn Left at Orion is a famous book, and in it, the writer instructs not to clean the mirror at all

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I believe that a general rule of thumb is not to clean a mirror for a year after it is (re)coated to allow the layers to fully harden, but after that it is relatively safe to do. With regards to the amount of dirt, that mirror didn't have enough to necessarily require it, but where the dirt is organic in nature, it is better to clean it so that it does not eat into the mirror coatings. The worst dirt is a finger print, which is most likely to get on the mirror immediately after you have finished cleaning it and necessitates starting the cleaning process again.

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On 25/08/2019 at 11:08, Ricochet said:

I believe that a general rule of thumb is not to clean a mirror for a year after it is (re)coated to allow the layers to fully harden, but after that it is relatively safe to do. With regards to the amount of dirt, that mirror didn't have enough to necessarily require it, but where the dirt is organic in nature, it is better to clean it so that it does not eat into the mirror coatings. The worst dirt is a finger print, which is most likely to get on the mirror immediately after you have finished cleaning it and necessitates starting the cleaning process again.

I had to clean my secondary mirror a few months ago - first time doing so. One site recommended wearing disposable surgical gloves to ensure no accidental deposits from your fingers end up on the mirror.

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An excellent cleaning job.

Although modern mirror cotings do seem to be tough, how do you know before you start?
Brillo pad the centre spot? Or the edges under the clips?

Even if you cleaned a particular make or type of scope and found it was an 'armoured' mirror, can you be sure every scope was made the same way?
Particularly as many mirrors are made in China these days.

No harm in being cautious.

David.

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I’d owned this mirror for a year and wanted to closely inspect it. On removal, as you can see the dust itself wasn’t excessive but the spider-webs were the main motivation to cause me to decide to clean it. Specifically trying to rid it of the glue-dabs the spiders use to attach the webs.

The secondary is actually dustier and the light when it reaches it is obviously more concentrated. My tactic with that so far has been simply to squirt de-ionized water from a plant-squirter down the focus-tube at it, with the main OTA pointing slightly downwards.

The freshly-cleaned primary had its first light last night, lovely views of M31 M32 M110 and M27 (my first view) and many more globs besides. A pristine dark night but as to whether I could tell any improvement, of course I could not, the views were all wonderful and bright but any difference would have been far too small without a lab-standard side by side comparison 

Next up I think I need to paint my focus-tube black, it protrudes into the main tube and is still naked aluminium-coloured.

Magnus

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Hi, i notice your locations includes SW Ireland? I just wanted to say my Father owns the family home in Brosna, Co.Kerry, SouthWest Ireland, and at night the light pollution is so low the sky is awash with stars etc. I dream to one day move out there and have the best veiws ever through m,y Telescopes. I currently live in Wavertree, Liverpool, which is awfully light polluted! I've genuinely considered breaking the law and cutting the power to the street lamps are are ruining my views! haha 

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On 22/08/2019 at 20:08, Captain Magenta said:

I've owned optics for decades and have cleaned front elements many times, but never, until now, a mirror.

A year or so ago I bought off @neil phillips his 300p Newtonian, and I must say I think it's a rather good mirror. He mentioned when I took it off him that "it holds collimation very well" and he was right. I've had three consecutive observing sessions, full removal from and attachment to mount each time, when I've not needed to adjust anything, using a Cheshire collimator.

It lives here in SW Ireland, and I'd resolved after a year to at least inspect the primary and see if it looked as though it needed a clean. There's been a bit of work done on the house here, bringing mucho dust, and there are also lots of spiders. Needless to say, once I'd removed it, there was evidence of much spider-action! I have no prior experience of whether mirrors need cleaning or not, but I judged this one was just the right side of spider-webbed and dusty that it could do with one?

A couple of rinses in detergent-water and eventual careful application of cotton-wipes rendered it more or less pristine. The final image below still shows a couple of stubborn spider-silk threads, but I let those go. It'll be interesting to see how it "views" when the clouds clear next...

Magnus

 

_MG_8266.jpg

_MG_8268.jpg

_S7A3576.jpg

_S7A3579.jpg

_S7A3588.jpg

Goodness me that really did need a good clean sir! It was covered in dust and cob webs! haha I'm 110% CERTAIN you will notice the difference in views when you next take her sky hopping! My Primary Mirror on my 5.1 inch Newtonian is a little dusty so i'm going to do same as you did and use detergent. There's some ace vids on YouTube about how to safely clean optics. I believe it's imperative that one doesn't rub the coatings off Mirror/Optics so one should use soft cotton extremely gently and only briefly. I'll post some pics of before, during and after. 

Open Skies to all... ( Wes, Liverpool, UK )

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1 hour ago, wesdon1 said:

Hi, i notice your locations includes SW Ireland? I just wanted to say my Father owns the family home in Brosna, Co.Kerry, SouthWest Ireland, and at night the light pollution is so low the sky is awash with stars etc. I dream to one day move out there and have the best veiws ever through m,y Telescopes. I currently live in Wavertree, Liverpool, which is awfully light polluted! I've genuinely considered breaking the law and cutting the power to the street lamps are are ruining my views! haha 

Yes awash with stars describes it. Last night walking back from pub with no Moon there were clear gaps in clouds wafting through, lovely sight. Tonight forecast clear so the 12” will be out.

Living in SW London area, the contrast between the two is fascinating. Have the bro in law with me who is interested so a bit of outreach in the offing...

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13 minutes ago, Captain Magenta said:

Yes awash with stars describes it. Last night walking back from pub with no Moon there were clear gaps in clouds wafting through, lovely sight. Tonight forecast clear so the 12” will be out.

Living in SW London area, the contrast between the two is fascinating. Have the bro in law with me who is interested so a bit of outreach in the offing...

oh it's beautiful over there. As you say the difference bewtween city pollution and over there in rural Ireland is amazing. and you lucky so n so having a 12 inch light bucket to veiw those amazing skies over there! lol I'm very jealous! lol

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... after another beautiful clear night last night, and seeing triangular diffraction patterns on low-altitude Star-tests, I decided to re-collimate my scope today. The overlapping mirror-clips themselves I had left loose before, but I’d over-tightened the horizontal grub-screws I think, so first off I loosened these and screwed them back in until they were just touching the mirror edge.

then I set about collimating everything from scratch. I brought the scope inside, and was very careful to avoid allowing any of our furry creatures into the tube.

So when I checked to see where they were, I realized Iorek was waaaaay ahead of me ...

 

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