A Blue 'Mist' on the Mirror of my Newt...?

[FLO]

On 27/06/2017 at 05:42, Dave In Vermont said:

I had the mirrors on my 200mm F/4 Newtonian re-mirrored about 2 years ago. And have now removed the secondary to fit a new focuser. And I just noticed strange blue-ish areas on the secondary.

...

Anyone have any ideas on what this is all about? I've never encountered such before.

 

On 28/06/2017 at 16:52, Dave In Vermont said:

I'm an organic-chemist.

I am a retailer, so might be wrong, but could it be the company you chose to re-aluminise your mirror have applied a protective overcoat to prevent the aluminium oxidising? 

I.e. Synta apply a protective layer of Silicon dioxide to their mirrors that can sometimes, if illuminated in a certain way, be seen as a petrol blue colour. It also sometimes shows when the mirror is dewed. 

HTH, 

Steve 

[JOC]

It looks to me like the remains of a plastic skin wrap left attached to the surface for too long and then peeled off.  It might be worth just running a finger nail around the edge of mirror to see if there was something you should have peeled off when you got the mirror back from the re-surfacing.  The trouble is, if it is organic in nature and it looks like it is, if you apply any solvent and the substance is still present on the mirror you might make things worse by chemically melting what is present onto the surface.  On the other hand if its a residue and the substance it came from is no longer around then an organic solvent might remove it. 

The following suggestions are what I would do, if it was a BASIC OBJECT - the fact that it is a telescope mirror means you might want to take advice from someone used to working with these very delicate surfaces which I HAVE NO EXPERIENCE OF.  If it is organic in origin - residue or otherwise then I doubt plain water will shift it though clearly its best to start light handed with water and work up.  I think I might be tempted to try just an edge (as small as possible) with a little solvent based glass cleaner - possibly a spectacle wipe, maybe some white vinegar, and sort of work up through the 'aggressive' nature of solvents until you find something that will shift it.  You should be able to wash any final solvent off by going via a mutually compatible solvent (maybe a clear IMS or even Vodka!) and then onto water.

[Dave In Vermont]

To Steve:

Very interesting hypothesis to chew on. So if I were to change the illumination source, it may vary and possibly even vanish? That's not a problem for me to look into. I'll put it on my list to hit it with everything from long-wave UV to red, green, and violet lasers, and even the old star up there itself. And whatever else pops into my craniums' birthing-chamber... Very interesting! This has now become a Research-Project, as well as a secondary-mirror for a 200mm F/4 Newtonian. Oh - the re-coating outfit I contracted is Majestic Optical Coatings - owned and oparated by Jeff Decker in Maryland, I believe. Feel free to re-contact if you have any other ideas fly through!

Thanks!

Ms. JOC:

I'll take a high-magnification view of this 'blue-mist' to see what details I can elucidate visually prior to using any solvent, as well as see what mild pressure and/or attempting to breach it's surface and see if the word "peel" is in it's vocabulary. As I said - this is now a Research-Project. All in in the name of science! <KaBOOM!!>

And hey - If I destroy the thing in my attempts at analysis, it's just a secondary-mirror. It's replacement won't cause me to starve for a month. Quite.....I wonder if the neighbor's Cat will share a few of her Mice with me...?

Thanks Folks - much appreciated -

Dave

[JOC]

1 hour ago, Dave In Vermont said:

I'll take a high-magnification view of this 'blue-mist' to see what details I can elucidate visually prior to using any solvent

Good idea.  I'm sure I've seen similar effects myself when a shiny surfaced object has lain touching a plastic surface which has become warm/hot over a long period.  The plastic sort of sticks to the surface and when you pull it away you seem to get a very similar looking effect - hence the thought that a layer of plastic might be involved.

 

I'm also reminded of the times I've purchased modern shiny objects and not realised there is a layer of 'sticky' plastic all over them to protect the surfaces - some are a real job to remove.  My 'glass' sound bar was covered in the stuff and it was really tricky to find and remove it all.

[FLO]

1 hour ago, Dave In Vermont said:

To Steve:

Very interesting hypothesis to chew on. So if I were to change the illumination source, it may vary and possibly even vanish?

If my guess is right (it is a protective overcoat) then yes. 

If it is not visible under normal light then I wouldn't worry. 

[Dave In Vermont]

Thus is how a theory is launched in science! Now for the proof.....

I've been suspecting the plastic all along, including prior to my writing this thread into existence. To your causative point: "...become warm/hot..." This doesn't match, but may well show something else - that temperature can be in normal 'room-temperature' and have this phenomena occur.

Very useful! Thanks!

Dave

[JOC]

2 minutes ago, Dave In Vermont said:

that temperature can be in normal 'room-temperature' and have this phenomena occur

I believe it could.  Because time is also an issue.  A warm environment would speed up the transfer of the residue, but plastics can break down just with plain ole 'time' and I would quite expect to see a residue effect if the plastic was present for a suitable duration even it is wasn't too warm.  For example, someone might have put something in a plastic bag for a year or so and returned to find it stuck to a surface.  Google says Vermont can regularly hit 80F that isn't chilly where plastics are involved.  I'm still only guessing, but I've packed a lot of lab-glassware in my time in the lab. 

[Plantins]

I had the same issue on a C14 Edge, Steve's right it's a protective coating (as far as the C14 Edge is concerned) and could only be seen when the primary was dewed up. It looks very similar to tape, as if there's some been stuck on the primary at some stage.

It doesn't look nice though and just looks poorly applied, whether it affects all units I don't know???

I've enclosed a photo of my C14 Edge which I got replaced at the time as no-one knew what it was (approx. 5 years ago) it also had the blue tinge which doesn't show up on this photo.

EDIT: Just to add the corrector plate or camera had nothing to do with the blue tinge colour on the primary.

[Dave In Vermont]

NO LONGER 'MYSTIFIED' -

I was planning to work on this again on the 5th, but my local 'Drug-Store' (Chemists) were out of distilled-water, so a delay was mandated. But today I had obtained the H2O I needed and set about trying to remove the 'blue-mist.'

First I applied the water with a drop of 'DAWN' dishwashing-liquid. This is considered the best for everything from burned lasagna to oil-soaked sea-birds some oil-tanker went aground next to their rookery. I applied this solution gently on a super-clean & sterile surgical cotton-pad. The 'blue' was seemingly a bit diminished. I thought this interesting, and wiped with a bit more pressure. The 'blue' still was there, and I thought I'd try something else - rather than apply yet more pressure.

With a fresh cotton-pad ready, I dried off the secondary-mirror with a bit of white-tissue. Then applied 91% iso-Propyl Alcohol to the fresh cotton-pad and ran this gently down the mirror. A good amount of the 'blue' vanished. Using a clean part of the cotton-pad, I went down the mirror again. Now most of the 'blue' vanished. I then essentially soaked the cotton-pad and soaked the mirror. The 'blue' was GONE!

I repeated this another time to ensure nothing remained behind in diluted form. And allowed the secondary to dry naturally after a light touch of a white-tissue.*

Looks to be fine now. Now to formulate a plan to address what this 'blue-mist' is/was that we are (or were) unknowingly adding to our diets. I have removed this plastic-wrap from my food-area. But intend to keep it as an example of why we should DRILL! DRILL! DRILL! for more oil! PLASTIC! It's What's for Dinner!

Thank you all for your ideas & suggestions! Hope we all learned a little something from this unwelcomed fiasco.

No Longer Blue,

Dave

 

* I used white-tissue so as not to introduce any chemical dyes to the area.

 

[JOC]

Yay!!  Well done Dave, I wondered if a bit of solvent might shift it - it certainly looked organic/hydrocarbon in origin so I'm not surprised that the IPA worked - as a solution it sounds a darn sight cheaper than buying another one!  I expect you are quite chuffed with the result.  Plastic wrap (disposal and longevity in landfills aside) for foods has to be 'food-safe' but the organics etc. that can be released as the plasticisers etc. breakdown are the reasons why it is sensible to not re-use plastics on food, and when you use them for covering things in the microwave make sure they are not in direct contact with the food.