jbeale
Well-known member
Lubricating is also an issue, because the lubrication could gas out and smeer the low pass filter.
Not every kind of lubrication necessarily has an outgas problem. For example Apiezon Grease T, vapor pressure @ 20C = 4.6x10-9 torr, melting point 125 C. Should cause no outgas problem unless you are shooting in ultrahigh vacuum.
Nnote, I have no idea whether this material is ok for aluminum surfaces, or generally suitable for use on a PL lens mount. If correct focusing really requires micron level precision, as I have read here that it does, I don't know how any grease could be used as it would form a variable thickness spacing layer between the metal surfaces.