The period of 1933–59 brought forth several improvements in the study of comets, which led to more discoveries and longer periods of visibility. The greatest advances came in the area of telescopes and photography.

Comet discoveries

The USA continued its dominance in discovering comets during this period, with amateur and professional astronomers being given official credit for 60 discoveries. Following the USA were South Africa (24 discoveries), Slovakia (19 discoveries), Japan (9 discoveries), Russia (8 discoveries), and Finland (7 discoveries).

The most prolific comet discoverer of this period was A. Mrkos (Slovakia), who found 11 new comets. Next in line were M. Honda (Japan) and L. C. Peltier (USA), who each found 7 new comets, M. J. Bester (South Africa), who found 6, and R. Burnham Jr. (USA) and D. du Toit (South Africa), who each found 5. Honda and Peltier were both amateur astronomers, while Burnham discovered comets as both an amateur and a professional astronomer.

Another important point concerning comets discovered during this period was that many were found during surveys. The most successful were the National Geographic–Palomar Observatory Sky Survey, which found 11 comets during the period of 1949–55, and the Skalnaté Pleso binocular comet search program, which found 19 comets during the period of 1948–59.

Comet observations

Several very active comet observers mentioned in Cometography volume 3 continued to observe during most, if not all, of the period covered by this volume. The most notable include G. van Biesbroeck, H. M. Jeffers, and M. Beyer.