Dr. Donald H. Menzel was the first to use the coronagraph in America. They are usually observed with a white-light coronagraph. The coronagraph was the flight spare of the white-light coronagraph on the OSO-7 satellite. An alternative would be to keep the coronagraph small. Dr. Bernard Lyot developed the first coronagraph to study the Sun's corona. The observatory also has a coronagraph, which is used to study the solar corona. The 1931 invention of the coronagraph allowed the corona to be studied in full daylight. The plasma is released into the solar wind, and can be observed in coronagraph imagery. Its main instrument will be a coronagraph for studying the dynamics of the solar corona. LASCO C3, the clear coronagraph picture, has a shutter time of about 19 seconds. A "band-limited coronagraph" uses a special kind of mask called a "band-limited mask". A stellar coronagraph concept was studied for flight on the canceled Terrestrial Planet Finder mission. Second, the telescope and coronagraph both incorporate several layers of wavefront control through active optics.