Assertion: newtonian telescope's mirror | /r/HasProperty | good
Facets:
value: very
type: DEGREE
Source sentences:
text: The view in these telescopes is narrow and unless the mirror is very good the image quality will suffer.
text: Buyers make sure: The main mirror and the secondary support plate must be very good quality as the optical lengthening of the focal length means that any errors in the mirror or plate are magnified!