Areas of sky approximately 1° × 1° square which were chosen by J. C. Kapteyn in 1906 for his study of the structure of the Galaxy. The 206 areas were uniformly spaced at about 15° intervals over the whole sky. In addition, 46 areas were chosen for their special significance in the Galaxy, such as the galactic pole regions. In each area the magnitudes, colours, spectral types, and proper motions of the stars were measured to as faint an apparent magnitude as possible.
Subjects: Astronomy and Astrophysics.