Assertion: telescope's use | /r/HasProperty | published as amateur telescope design
Facets:
value: in a f/15 and f/23 variation
type: OTHER
Source sentences:
text: Commercial use of Gregory's design was explicitly reserved for Perkin–Elmer but was published as an amateur telescope design in a 1957 issue of Sky and Telescope in a f/15 and f/23 variation.