van den Bergh galaxy classification

The van den Bergh galaxy classification is a variant on the usual galaxy classification (Hubble sequence) that appends an indication of the galaxy's luminosity, the van den Bergh luminosity classification, which classifies galaxy luminosity in nine classifications, from Roman numerals I (brightest) to V (faintest, i.e., dwarf galaxies), with intervening classes labeled "I-II", "II-III", etc. Van den Bergh developed the classes for galaxies in the POSS plates (for use in the David Dunlap Observatory Catalog), and noted an association between these luminosity classes, and the galaxies' morphology, particularly the spiral structure of spiral galaxies.