This webpage gives an overview of the cleaning possibilities of various optical components
Cleaning optical components
Dust is very abrasive and should be blown off all components before any other cleaning. Use dry nitrogen (with critical components like large mirrors, avoid using a can, these can squirt out liquid). Blowing dust off gratings should be done very gently, otherwise there is risk of damage.
1. Glass-covered filters, coloured-glass filters and lenses
Filters can be cleaned with Balzer’s No. 2 and tissue or preferably a lint-free cloth, or OPTICLEAN
The ISIS dichroics have unprotected coatings. No cleaning should be attempted
3. Unprotected aluminium mirrors
Dust can be removed by blowing off with nitrogen, or with water + detergent (or with CO2 snow, on large mirrors). Cloth should never be used. The WHT Nasmyth flat was recently cleaned successfully by PL25, a spray-on, peel-off product.
4. Overcoated mirrors
E.g. ISIS camera and collimator mirrors (overcoated silver in the red, overcoated aluminium in the blue) and fold mirrors (both overcoated quartz). Dust should be removed floated off with water + detergent or iso-propyl alcohol, standing the component on the edge to drain. Overcoated mirrors (such as the ISIS camera and collimator mirrors) can be cleaned with a very wet optical grade cloth (e.g. Balzer’s cloth) soaked in Balzer’s No. 2 (removes grease) or OPTICLEAN (removes grease and dust). OPTICLEAN is usually used on smaller components.
5. Polished steel
E.g. ISIS slit jaws. Clean as overcoated mirrors. Dust on slit jaws should come away when solvent is used.
6. Gratings
Apart from gently blowing away dust, no further cleaning is possible; the slightest abrasion will increase scattered light. Scratches should be left alone; they could be painted out (matt black) but RGO advises against it.
/Chris Benn 1993 Apr 8 - based on the advices of Sue Worswick and Dave Jackson/