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 "Christ ist erstanden" and "Nun bitten wir den Heiligen Geist" adapted original Gregorian melodies to translated texts. Secular tunes such as the popular Renaissance "In Nomine" were based on Gregorian melodies. Beginning with the improvised harmonizations of Gregorian chant known as organum, Gregorian chants became a driving force in medieval and Renaissance polyphony. Often, a Gregorian chant (sometimes in modified form) would be used as a "cantus firmus", so that the consecutive notes of the chant determined the harmonic progression. The Marian antiphons, especially "Alma Redemptoris Mater", were frequently arranged by Renaissance composers. The use of chant as a cantus