Argelander's work was continued for stars between δ = -2° and δ = -23° by Schönfeld, according to much the same plan, but with a larger instrument (aperture 159 mm, focal length 1930 mm, magnifying power 26 times). The observations were made in the years 1876 to 1881 and include 133659 stars.[8]
The positions in B. D. are given in tenths of a second in right ascension and in tenths of a minute in declination.
20.
The Cape Photographic Durchmusterung[9] (C. P. D.). This embraces the whole southern sky from -18° to the south pole. Planned by Gill, the photographs were taken at the Cape Observatory with a Dallmeyer lens with 15 cm. aperture and a focal-length of 135 cm. Plates of 30 × 30 cm. give the coordinates for a surface of 5 × 5 square degrees. The photographs were taken in the years 1885 to 1890. The measurements of the plates were made by Kapteyn in Groningen with a “parallactic” measuring-apparatus specially constructed for this purpose, which permits of the direct obtaining of the right ascension and the declination of the stars. The measurements were made in the years 1886 to 1898. The catalogue was published in three parts in the years 1896 to 1900.
The positions have the same accuracy as in B. D. The whole number of stars is 454875. Kapteyn considers the catalogue complete to at least the magnitude 9m.2.
In the two great catalogues B. D. and C. P. D. we have all stars registered down to the magnitude 9.0 (visually) and a good way below this limit. Probably as far as to 10m.
A third great Durchmusterung has for some time been in preparation at Cordoba in Argentina.[10] It continues the southern zones of Schönfeld and is for the present completed up to 62° southern declination.
All these Durchmusterungs are ultimately based on star catalogues of smaller extent and of great precision. Of these catalogues we shall not here speak (Compare, however, [§23]).
A great “Durchmusterung”, that will include all stars to the 11th magnitude, has for the last thirty years been in progress at different observatories proposed by the congress in Paris, 1888. The observations proceed very irregularly, and there is little prospect of getting the work finished in an appreciable time.