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
Conversion between Julian and Gregorian calendars but earlier than, the date to be converted. Be sure to use the correct column. If converting from Julian to Gregorian, add the number from the "Difference" column. If converting from Gregorian to Julian, subtract. Conversion between Julian and Gregorian calendars The tables below list equivalent dates in the Julian and Gregorian calendars. Years are given in astronomical year numbering. This table is taken from the book by the Nautical almanac offices of the United Kingdom and United States originally published in 1961. Dates near leap days that are observed in the Julian calendar but not in the Gregorian are