Cleaning a 6" RC primary

[Mcwaffles2003]

So I'm an idiot. I saw some dust on my primary and tried to blow it out with a hand squeeze air blaster but the mirrors pretty deep and it was doing nothing... So I tried to use computer duster... and blasted my mirror with the oil (i believe its a type of oil) from in the can and now there's a bunch of spots on my mirror. How do I go about cleaning my mirror? would disassembling my OTA be a bad move? I'm at a loss here, seriously any advice would be  

[Ruud]

Sorry about what happened! I can't see any other way of cleaning this mirror without taking it out.

The surface of the mirror is probably very sensitive to scratching and dulling. A safe way of cleaning Newtonian mirrors is by soaking them in a soapy solution, placing them under a running tap, more of the same if needed and finally rinsing with distilled water. Then you let the water run off the mirror. There are youtube videos showing this.

Best is not to touch the mirror at all. If you can't get this goo off by soaking and rinsing alone, consider gently stroking it while submerged in its soapy bath with cotton, applying zero pressure.

The mirror is enhanced coated aluminium.  I've wet cleaned an enhanced coated diagonal at least a half dozen times without any trace of deterioration, but that was very easy to remove and put back. Unfortunately you don't have that luxury.

If you see no way of getting the mirror off the baffle, there is a far less preferred way of cleaning it with some very soft material moistened with a solvent. If you do that just once you may not notice any damage it causes. You will cause micro scratches though.

Personally, I would send the telescope back for a professional cleaning.

[Mcwaffles2003]

I'm not too scared about the act of cleaning itself. I have watched some videos demonstrating cleaning mirrors by submerging them in a water bath with 1 maybe 2 drops of soap. If the obstruction doesnt clear from this then floating cotton balls and sloshing the entire tub gently so the cotton balls move back and fourth to "scrub" the mirror with absolutely no pressure. then acetone or isopropyl alcohol mixed with water rinse followed by a DI water rinse. All in all I would actually like to learn this skill myself as I assume I will need to clean another mirror in the, hopefully distant, future.

What I need help understanding is the disassembly process. I am guessing i would undo the screws toward the back of the scope (near where the white and black materials meet in the 2nd image). then i assumbe the back could be removed but then how would i detatch the mirror from the part of the OTA its attached to? does it simply screw off? Also, when reassembling the scope will I have ruined the primary to secondary distance? Will this distance even make a drastic difference in my seeing ability with very slight changes in distance?

[Ruud]

Maybe this helps, someone removes an RC primary mirror, but you have a different brand and size telescope, so this can only serve as an idea of what you may expect:

 

[Mcwaffles2003]

beyond helpful, thank you so much

[Mcwaffles2003]

So, to anyone that comes across this in the future, an update on the topic. I followed the disassembly through the video above:

7 hours ago, Ruud said:

Maybe this helps, someone removes an RC primary mirror, but you have a different brand and size telescope, so this can only serve as an idea of what you may expect:

 

Then when it came to cleaning the mirror i followed the instruction from here:

My first attempt strictly following the cleaning video resulted with the picture below with the blue smearing. I almost freaked out thinking Ive done something amazingly wrong to the mirror. I came back to it after a moment of recollection and went through the process again. but this time towards the end i began to clean using acetone in the water with the floating cotton ball method. I then rinsed with pure acetone which quickly dried leaving very little residue (still some) and almost no more blue smear. At this point I said I've pushed my luck enough and reassembled the telescope giving the final image. Not perfect, but much better than when I started.

 

To all, from my new born experience, I direly urge you...

 

 NEVER USE COMPUTER DUSTER TO DUST OFF A MIRROR... YOU WILL HAVE A BAD TIME!!!

[Ruud]

Definitely better. Much better. Maybe, one day, you'll get it as clean as it once was. Meanwhile I hope the mirror performs to satisfaction! 

[LukeSkywatcher]

Looks good. I agree that air in a can is NOT a good way to clean mirrors. 

Why?

The compressed air uses a propellant to get it out of the can. This (as you found out) leaves a nasty residue.

Im not sure i'd like to use acetone either. Its an acid and could eat away the coating on mirrors. Im not saying it will. Ive just never heard of it used before. De-ionized water is usually the recommended cleaning agent and a drop of washing up liquid.

Baader Wonder fluid is brilliant.

[Sunshine]

Your mirror should not need anymore cleaning again unless you drop your slice of pizza into the tube, mirrors need to be messed up pretty bad to justify a cleaning, ignore dust. 

[Mcwaffles2003]

10 hours ago, LukeSkywatcher said:

Looks good. I agree that air in a can is NOT a good way to clean mirrors. 

Why?

The compressed air uses a propellant to get it out of the can. This (as you found out) leaves a nasty residue.

Im not sure i'd like to use acetone either. Its an acid and could eat away the coating on mirrors. Im not saying it will. Ive just never heard of it used before. De-ionized water is usually the recommended cleaning agent and a drop of washing up liquid.

Baader Wonder fluid is brilliant.

Acetone isnt an acid but a volatile organic compound, like alcohol. I originally attempted using distilled water but upon contact with the mirror it seemed to leave a residue. I assume the residue was from the soluble salts in sink water instantly falling out of solution upon cooling when mixing with the cool DI water. The acetone seemed to do a much better job of instantly removing the old sink water away from the mirrors surface and it left the surface dry in under 10 seconds. 

 

11 hours ago, Ruud said:

Definitely better. Much better. Maybe, one day, you'll get it as clean as it once was. Meanwhile I hope the mirror performs to satisfaction! 

Hopefully I wont have to try at it for a long time.

5 hours ago, Sunshine said:

Your mirror should not need anymore cleaning again unless you drop your slice of pizza into the tube, mirrors need to be messed up pretty bad to justify a cleaning, ignore dust. 

Lets hope I dont do anything so dumb again, though I believe I was justified with my urge to clean after this mishap shown in my 1st pic

 

Im a bit insecure about the bits on my secondary I have discovered (as seen in the reflection of my final pic), but that seems like it would be a bit harder to separate from the OTA and I think Ive pushed my luck enough. Hopefully those little bits wont create too noticeable of an impact

[JOC]

Acetone is an organic solvent.  The simplest ketone.  In it's pure form it does not possess the free hydrogen ions needed to generate pH and must therefore be considered neutral.  I cannot see any  reason why pure acetone should be detrimental to a mirrored surface.  Acetone or simlar solvents are useful in that they are miscible with and can therefore remove  water residues and are volatile enough to evaporate quickly leaving, theoretically, no residue themselves.  I haven't ever seen a bottle of it, but I bet Baader wonder fluid is just a pure similar organic solvent.

It is worth remembering that neither distilled or deionised water will totally evaporate without leaving a residue.  Distilled deionised water is about as good as you will likely buy, but it is still not residue free pure water.  IMO you will still be better off finishing off with a water miscible organic solvent like PURE acetone if you can get hold of it.  Note pure acetone is not nail varnish remover which is full of 'nail conditioners'!

[AKB]

27 minutes ago, JOC said:

I haven't ever seen a bottle of it,

Really?  I got some over the counter at Boots...

[Ruud]

Ha! My bottle is much bigger!

It's good to have, but be careful. It dissolves plastics. Only use it as a last resort.

 

[Louis D]

Acetone and other solvents are pretty cheap to buy in quart and gallon sizes at big box home improvement stores.  Xylene is much more aggressive than acetone, I've found.  I keep both around when trying to remove goo.

[JOC]

No, I meant I hadn't seen a bottle of Baader wonder fluid!! Lol. Acetone I used to mess around with in Winchester bottle quantities!

[Ruud]

It's a boring little bottle and way overpriced. Ethanol 25% and propanol 35%. About €100 per liter.

 

[JOC]

15 hours ago, Ruud said:

Ethanol 25% and propanol 35%

Just a bottle of mixed solvents (alcohols - I was actually going to suggest that methanol would probably be a good bet if you could get it as it is miscible with organics and water and is often used as a common solvent to go between the two and would also evaporate - if that's what's in Wonder fluid then I bet Methanol would be a good option)  then just as I expected.  Acetone, clear Industrial methylated spirits, The 'oil' stain devil product, or probably the large bottle of JML screen cleaner you can often buy in discount stores would probably be just as good.  NB.  All these organic solvents need handling with an appropriately resistant pair of gloves and safety glasses.

[JOC]

NB.  The old canned air duster that you use on a PC would have probably been OK, but I bet you turned if off horizontal when you used it.  All canned air dusters should be handled always with the cans horizontal otherwise the often liquid under pressure propellant itself can be expelled over what you are dusting.  This is as true for a telescope lens as for the insides of your computer!

[Louis D]

10 hours ago, JOC said:

All canned air dusters should be handled always with the cans horizontal otherwise the often liquid under pressure propellant itself can be expelled over what you are dusting.

Did you mean to say vertical?

[JOC]

9 hours ago, Louis D said:

Did you mean to say vertical

I meant horizontal with respect to the contents that they contained - in the same way that you hold a jug horizontal, if you hold it vertically the contents fall out.  With the air duster if you hold it so the contents stay in the bottom of the can they are less likely to expel the propellant through the aerosol.

[jfox61]

You hold a jug vertically as you do an aerosol can.  Lying a jug on its side would mean it was horizontal and therefore release its contents. As for aerosol cans, it matters not how you hold them you will always expel  propellant along with whatever other agent is in there. Not only that but due to the fall in pressure when using aerosol cans you will get water vapour expelled too.

[Louis D]

IIRC, professional observatories blast their giant mirrors with CO2 charged fire extinguishers (sort of) to blow dust off of them.

[JOC]

Ok, so you hold the air duster can err.....upright!   :-)

[Mcwaffles2003]

On 3/17/2018 at 13:10, JOC said:

Acetone is an organic solvent.  The simplest ketone.  In it's pure form it does not possess the free hydrogen ions needed to generate pH and must therefore be considered neutral.  I cannot see any  reason why pure acetone should be detrimental to a mirrored surface.  Acetone or simlar solvents are useful in that they are miscible with and can therefore remove  water residues and are volatile enough to evaporate quickly leaving, theoretically, no residue themselves.  I haven't ever seen a bottle of it, but I bet Baader wonder fluid is just a pure similar organic solvent.

It is worth remembering that neither distilled or deionised water will totally evaporate without leaving a residue.  Distilled deionised water is about as good as you will likely buy, but it is still not residue free pure water.  IMO you will still be better off finishing off with a water miscible organic solvent like PURE acetone if you can get hold of it.  Note pure acetone is not nail varnish remover which is full of 'nail conditioners'!

https://www.homedepot.com/s/acetone?NCNI-5

it may not be 100% pure but it is pretty close, if you want pure Im guessing you could look into getting some from sigma aldrich. theyre a well know chemical supply store for labratories. although the home depot stuff did a fine job

On 3/17/2018 at 13:38, AKB said:

Really?  I got some over the counter at Boots...

how much did they charge you for that

 

6 hours ago, Louis D said:

IIRC, professional observatories blast their giant mirrors with CO2 charged fire extinguishers (sort of) to blow dust off of them.

thats kinda crazy as the white smokey looking stuff that comes out  is fine particulate dry ice

 

On 3/17/2018 at 14:07, Ruud said:

Ha! My bottle is much bigger!

It's good to have, but be careful. It dissolves plastics. Only use it as a last resort.

 

good thing my mirror isnt made of plastic :P. ironically acetone can be used to make plastics as well.

[Mcwaffles2003]

On 3/18/2018 at 11:01, JOC said:

Just a bottle of mixed solvents (alcohols - I was actually going to suggest that methanol would probably be a good bet if you could get it as it is miscible with organics and water and is often used as a common solvent to go between the two and would also evaporate - if that's what's in Wonder fluid then I bet Methanol would be a good option)  then just as I expected.  Acetone, clear Industrial methylated spirits, The 'oil' stain devil product, or probably the large bottle of JML screen cleaner you can often buy in discount stores would probably be just as good.  NB.  All these organic solvents need handling with an appropriately resistant pair of gloves and safety glasses.

The gloves comment is a good point. As I was using nitrile gloves I noticed that the glove of my right hand had become far more elastic and thinner after being doused with acetone. I believe this would be the case with either latex or vinyl as well but more so.