20D/Westphal was a periodic comet with an orbital period of 61 years. It fits the classical definition of a Halley-type comet with (20 years < period < 200 years). It was originally discovered by the German astronomer J. G. Westphal (Göttingen, Germany) on July 24, 1852. It was independently discovered by the American astronomer Christian Heinrich Friedrich Peters (Constantinople) on August 9. The comet was last seen between September 27 and November 26, 1913, first by Pablo T. Delavan (La Plata Astronomical Observatory) and then others. It was predicted to return in 1976 but was never observed, and is now considered a lost comet. References External links Orbital simulation from JPL (Java) / Horizons Ephemeris 20D/Westphal, Comet Orbit Home Page 20D at Kronk's Cometography Orbital elements, Infrared Processing and Analysis Center 20D/Westphal – Minor Planet Center Periodic comets Halley-type comets 0020 020D Lost comets 18520724