I am being told by several VERY experienced observers in our club that the enhanced coatings on our 30" mirror would need to be GROUND off to apply a new coating. This would necessitate refiguring and polishing and many other headaches(the mirror has a central hole). Has anyone heard of a coating that needs to be ground off?
Grinding off enhanced coatings?
Started by sthater, 07/02/2003 03:21PM
Posted 07/02/2003 03:21PM
Opening Post
Posted 07/02/2003 03:55PM
#1
Yes, this may be true. If your mirror has a "coating" from electron beam deposition (e.g. sputtering from a cathode in a vacuum chamber), it is very durable and has properties which exclude conventional chemical coating removal.
As an example, the dielectric mirror diagonals from AP and TeleVue have very hard finishes, using the same multi-layer beam technology developed for tank optics which are cleaned often in a desert environment.
Perhaps "grinding" is a bit strong and "polishing" could accomplish the same task more gently.
See this description of sputtering processes used for one of the Keck optics:
http://www-eng.llnl.gov/silver_mirror/pdf/Hawaii_8_2002.pdf
As an example, the dielectric mirror diagonals from AP and TeleVue have very hard finishes, using the same multi-layer beam technology developed for tank optics which are cleaned often in a desert environment.
Perhaps "grinding" is a bit strong and "polishing" could accomplish the same task more gently.
See this description of sputtering processes used for one of the Keck optics:
http://www-eng.llnl.gov/silver_mirror/pdf/Hawaii_8_2002.pdf
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