Gill's collaboration with Kapteyn on the Cape Photographic Durchmusterung
(CPD) and subsequent repeat observations had led to the discovery of two "star streams", or preferential groups of proper motions, shared by certain stars [now known to be a reflection of halo and disc populations or old and young stars].
The Cordoba Durchmusterung
published, containing 580,000 stars.
The variability of T Ursae Majoris was discovered in 1860 by the astronomers at Bonn Observatory in Germany who were compiling the great Bonner Durchmusterung
star catalog and atlas.
The immediate outcome was the Cape Photographic Durchmusterung
which gives the approximate positions and brightness of nearly half a million southern stars.
Among the most important 19th century surveys were the Bonner Durchmusterung
(BD) of Argelander and the Cape Photographic Durchmusterung
(CPD) of Gill and Kapteyn.
The month before his discovery of V Cas, he had also reported that another star listed in the Bonner Durchmusterung
as being of magnitude 8.
This star's variability was discovered at Bonn Observatory in Germany in the mid-19th century while astronomers were compiling the great Bonner Durchmusterung
Pickering noted in the publication of his A Durchmusterung
of Variable Stars, that the value of visual observations of variable stars was no longer centred on the individual's attention to a single star, but on the recruitment of many observers who were able to observe as many stars as possible.
The first photographically produced catalogue of stars, the Cape Photographic Durchmusterung
(CPD), was the brainchild of David Gill, Her Majesty's Astronomer at the Cape in the years 1879-1907.
150 ya, in 1859, publication of the Bonner Durchmusterung
The resulting catalog, the Cape Photographic Durchmusterung
(CPD), contained positions and magnitude estimates for 454,875 stars.
One had to select stars from the BD (Bonner Durchmusterung