odern astrophysics owes its existence to small-telescope surveys dating back to the 18th century, for example
Flamsteed (1725). In the 19th century, Argelander’s survey based on visual observations with small telescopes
and meridian circles culminated in the 1859 publication of the Bonner Durchmusterung (BD), a catalogue of
northern hemisphere stars brighter than ninth magnitude, with accompanying charts (Batten 1991). The BD
catalogue was later extended to the southern hemisphere by the Córdoba Durchmusterung (CD; 1892 onwards)
prepared using Argelander’s method, and the Cape Photographic Durchmusterung (CPD; 1885onwards) based on
photographic plates.