Reflective Objective

[microb]

For an IR reflective objective, the large mirror is fine, but the smaller center mirror looks foggy. Does anyone have recommendations? This is a Thermo Spectrum objective, so I don't know what coatings if any would have been done back in the early 2000 time frame.

For another project, I might mill an aluminum mirror and since some telescope people are around, where do they go to get an aluminum mirror coated to be an enhanced aluminum surface?

[apochronaut]

Mirror objectives seem ill suited to use with standard refractive condensers. Systems were sold where the condenser was a mirror image of the objective.

[microb]

Mirror objectives seem ill suited to use with standard refractive condensers. Systems were sold where the condenser was a mirror image of the objective.

Correction on my part, I had taken the unit apart so long ago, I had forgotten about the condenser, which had screws fallen into it. But yes, this did have a transmission set up with a parabolic mirror below.

[dtsh]

For an IR reflective objective, the large mirror is fine, but the smaller center mirror looks foggy. Does anyone have recommendations? This is a Thermo Spectrum objective, so I don't know what coatings if any would have been done back in the early 2000 time frame.

For another project, I might mill an aluminum mirror and since some telescope people are around, where do they go to get an aluminum mirror coated to be an enhanced aluminum surface?

If it just needs to have the aluminum redone, that should be pretty easy. I haven't needed to strip a mirror yet, but I seem to recall various methods being discussed from NaOH to HCL. I'd pop over to cloudynights.com or peruse the ATM books if you have them to be sure. As for where to get the aluminum coating redone, I suspect that's going to be regional. Again, a query over at cloudynights.com would probably yield a list of coaters on your continent faster than anything else. It looks to be a small part, so should be very easy. If you're brave I can share the information I have on the process; in a nutshell, it's mostly just a matter of electrically evaporating bits of aluminum in a vacuum; haven't done it myself, but was looking into it a few years ago when I ground my last mirror.
I can't even begin to speculate on what other possible coatings it might have.

[Chris Dee]

I know there are a few companies here that offer sputter deposition services. Might be one near you Bob, or maybe an academic facility?

[hans]

There was a thread about trying to restore the mirror coating on a darkfield condenser earlier this year:
https://www.microbehunter.com/microscop ... =5&t=11850

[patta]

Only thing I know, DO NOT WIPE IT. Wiping will scratch the mirror.
Maybe the mirror is ok, just extra dirty by fat droplets or other things deposited and sturdily clinging on it. Soak it with mild soap, or other liquids like alcol or acetone; if that fix the foggyness, great, no need for re-coating . Wish you luck. Anyway, Never touch it! Experience from scratching many mirrors. So much softer than glass.
If really the goo doesn't move, ok let's rub it - with the cleanest cotton available; but before, make sure all other options to remove particles have been exhausted: hot running water, compressed air, even WD-40 followed by hot soap bath. Until the glue that is holding it holds...
My guess is that both mirrors would have been made with same substrate and same coating; the small one got deposits of dust etc because it's facing upwards.

For the dIY aluminium mirrors - some more bragging: aluminium can get pretty flat and mirror reflective if milled / polished to low roughness. I don't think a further coat would give much more. Fine sandpaper and some intense buffing should do.. Lamp collectors are often made from a bare aluminium cup, well buffed.
The "enhanced aluminium surface" I think means normally an hard coat over the metal, just to protect it. Magnesium fluoride often, the same as standard antireflection coating for lenses. Most optical workshop can do that - but they'll be very unenthusiast to do the job, as your piece of aluminium may be full of oil and contaminants, that will ruin their vacuum coating oven. For some applications they put a dielectric multilayer-like coating - so to improve the reflectivity, from 90% of bare aluminum to a whopping 95% for the enhanced coating. I would rather go for a 5% increase in lamp power but is surely fun to get in contact with optical workshops. Painting yourself the aluminium with a normal transparent varnish may be a valid alternative too.

[microb]

Mirror objectives seem ill suited to use with standard refractive condensers. Systems were sold where the condenser was a mirror image of the objective.

So I had taken this unit apart last year, and I forgot about the condenser. So went through the packed parts, and yep there was a condenser and it couldn't turn.

So I'm soaking that too. Here it is in iso.

Would a modern set-up just use IR optics? And would they need a special IR glass for the condenser? Edmond Optics sells reflective objectives, but maybe I missed finding the reflective condensers to match.

[microb]

I guess they are spherical mirrors:

https://spie.org/publications/tt48_376_ ... hild?SSO=1

[microb]

https://jascoinc.com/learning-center/th ... icroscopy/

[patta]

I think Beck of UK was and may still be the main designer and manufacturer:

https://www.beckoptronic.com/support/

The first pdf is great. Spherical, they don't say, but most probably. I didn't have the patience of reading the reference papers...