Assertion: newtonian telescope's mirror | /r/CapableOf | coat with protective layer of quartz
Facets:
value: for long life
type: TEMPORAL
Source sentences:
text: Both internal mirrors, primary and secondary, are ground and polished under computer control for guaranteed diffraction limited performance then coated with 91% reflectivity enhanced aluminum, and then coated again with a protective layer of quartz for long life.