Cas seg rain i an (kasegranian)

Relating to one Ca egrain, who in 1672 described a new form of reflecting telescope e entially different from those of Newton and Gregory. There is a hole at the center of the large mirror (as in the Gre. gori an form), but the rays leaving that mirror, before coming to a focus, strike a small convex mirror, and are reflected through the hole to the eyepiece. The telescope is shorter than the Greg or i an, the spherical aberration is partly eliminated, and the lo of light is about that of the Newton i an. See telescope. Ca el brown, green, etc. See the nouns. Ca elmann's green. See green. ca en (kas'en). An English dialectal form of the past participle of cast1.