Schmidt camera optical axis of the Schmidt design creates a Schmidt-Newtonian telescope. The addition of a convex secondary mirror to the Schmidt design directing light through a hole in the primary mirror creates a Schmidt-Cassegrain telescope. The last two designs are popular with telescope manufacturers because they are compact and use simple spherical optics. A short list of notable and/or large aperture Schmidt cameras. Schmidt camera A Schmidt camera, also referred to as the Schmidt telescope, is a catadioptric astrophotographic telescope designed to provide wide fields of view with limited aberrations. The design was invented by Bernhard Schmidt in 1930. Some notable
Gregorian chant focusing on octaves, fifths, fourths, and, later, thirds. Neither tropes nor organum, however, belong to the chant repertory proper. The main exception to this is the sequence, whose origins lay in troping the extended melisma of Alleluia chants known as the jubilus, but the sequences, like the tropes, were later officially suppressed. The Council of Trent struck sequences from the Gregorian corpus, except those for Easter, Pentecost, Corpus Christi and All Souls' Day. Not much is known about the particular vocal stylings or performance practices used for Gregorian chant in the Middle Ages. On occasion, the clergy was urged to