The special silicone optical coupling grease is special and expensive stuff. Needless to say it is not absolutely necessary, but saves on losses found in the surface-air-surface transmission of the few photos in the event. I don't think vacuum silicone grease will work for this. It is milky and the proper stuff the much less viscous and water clear.
Richard Hull
Created on Monday, April 16, 2001 2:06 AM EDT by Richard Hull