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 Multi-voice elaborations of Gregorian chant, known as organum, were an early stage in the development of Western polyphony. Gregorian chant was traditionally sung by choirs of men and boys in churches, or by men and women of religious orders in their chapels. It is the music of the Roman Rite, performed in the Mass and the monastic Office. Although Gregorian chant supplanted or marginalized the other indigenous plainchant traditions of the Christian West to become the official music of the Christian liturgy, Ambrosian chant still continues in use in Milan, and there are musicologists exploring both that and the Mozarabic