Ernst Dinkla wrote:
The cone will be taken off the instrument before the cleaning. It is a simple part with a 0.55mm selected white float glass disc glued in at the wide side. One expects that the UV cut version will have the filter glass there. I guess Vladimir uses one of the clean air pressurised cans to blow the dust out, you wouldn't like to use 8 bar air with oil mist for that purpose.
I use a very thin brush to clean the inner side of the cone -- works like a charm. I've had bad experience of compressed air in cans: they can spray propellant drops that leave stains behind on optical surfaces.