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Cassini (with the Washbowl and its Plughole)

Lat: 40.21°N, Long: 4.59°E, Diam: 56.39 km, Depth: 1.24 km, Rukl: 12, Lower Imbrian

external image normal_cassini2006-10-12a.jpg
Mario Weigand Cassini is the large ring in the center. The lettered craters associated with Cassini that are visible in Mario’s view are Cassini A (the oddly shaped 15 km crater near the center of Cassini), Cassini B (to the west of Cassini A), Cassini M (outside Cassini’s ring to the north) and 7-km Cassini F (on the extreme right, in the part of Mare Imbrium once known as Palus Nebularum).


LPOD Photo Gallery Lunar Orbiter Images Apollo Images Wes Higgins

  • Although the name Cassini is not included in the LPI's searchlist of orbital Apollo photographs, it WAS frequently photographed during the mission of Apollo 15! Cassini is noticeable on several frames in Apollo 15's only north-looking Fairchild mapping/metric camera magazine Revolution 35. For example: on Fairchild frame AS15-M-1538, Cassini is visible very near the "vertical" part of the curved horizon (at the central part of the depicted horizon).
    • Research: Danny Caes


(LAC zone 25B3) LAC map Geologic map



(IAU Directions) CASSINI.--This remarkable ring-plain, about 36 miles in diameter, is very similar in character to Posidonius. It has a very narrow wall, nowhere more than 4,000 feet in height, and falling on the W. to 1,500 feet. Though a prominent and beautiful object under a low sun, its attenuated border and the tone of the floor, which scarcely differs from that of the surrounding surface, render it difficult to trace under a high angle of illumination, and perhaps accounts for the fact that it escaped the notice of Hevel and Riccioli; though it is certainly strange that a formation which is thrown into such strong relief at sunrise and sunset should have been overlooked, while others hardly more prominent at these times have been drawn and described. The outline of Cassini is clearly polygonal, being made up of several rectilineal sections. The interior, nearly at the same level as the outside country, includes a large bright ring-plain, A, 9 miles in diameter and 2,600 feet in depth, which has a good-sized crater on the S. edge of a great bank which extends from the S.E. side of this ring-plain to the wall. On the W. side of the floor, close to the inner foot of the border, is a bright deep crater about two- thirds of the diameter of A, and between it and the latter Brenner has seen three small hills. The outer slope of Cassini includes much detail. On the S.E. is a row of shallow depressions just below the crest of the wall, and near the foot of the slope is a large circular shallow depression associated with a valley which runs partly round it. The shape of the glacis on the E. is especially noteworthy, the S.E. and N.E. sides meeting at a slightly acute angle at a point 10 or 12 miles E. of the summit of the ring. On the outer W. slope is a curious elongated depression, and on the N. slope two large dusky rings, well shown by Schmidt, but omitted in other maps. Most of these details are well within the scope of moderate apertures. Perhaps the most striking view of Cassini and its surroundings is obtained when the morning terminator is on the central meridian.



Additional Information

  • IAU page: Cassini
  • Depth data from Kurt Fisher database
    • Westfall, 2000: 1.24 km
    • Viscardy, 1985: 1.24 km
    • Cherrington, 1969: 1.06 km
  • Nearby concentric crater
  • Knopp observed red patches in Cassini on 21st February 1885. Source: V.A.Firsoff's The Old Moon and the New (1969), page 185.- DannyCaes May 19, 2012


  • This crater currently honors two men:
    • Giovanni Domenico Cassini (June 8, 1625–September 14, 1712) was an Italian-French astronomer, engineer, and astrologer. Cassini, also known as Giandomenico Cassini and Jean-Dominique Cassini (not to be confused with great grandson of the same name), was born in Perinaldo, nearby Sanremo, at that time in the Republic of Genoa. Cassini was instrumental in the founding of the Paris Observatory, which he directed, and, among his many other accomplishments, produced two noteworthy lunar maps. The larger and more detailed of the two appeared in 1679; but a smaller version published in 1692 was much more widely distributed and copied (Whitaker, pp. 78-80). According to Launay and Sheehan (2010), 60 carefully dated large chalk and and pencil drawings of the Moon prepared by professional artists as part of the Moon mapping project are preserved in an album at the Paris Observatory.
      • The Paris Observatory's original print of Cassini's 1679 Large map of the Moon was displayed along with two of the drawings by Sébastien Leclerc and Jean Patigny at a 2009 exhibit in Florence.
    • Jacques Cassini (February 8, 1677 - April 18, 1756) was a French-Italian astronomer, son of the famous Italian astronomer Giovanni Domenico Cassini. He succeeded his father as director of the Paris Observatory, as did one of his own sons and grandsons.
  • According to Whitaker (p. 92), the name Cassini was introduced on a map by Allard from 1700, but it was used for a crater other than the present one. The present crater was named J.D. Cassini by Schröter (Whitaker, p. 218). The "J.D." part seems to have been dropped by later observers and was never part of the IAU nomenclature.
  • In the original IAU nomenclature of Blagg and Müller (1935), J. J. Cassini was commemorated by a separate crater (with two satellites) at 73°N/20°W, with the name shortened to J. Cassini by Kuiper in 1961. Shortly thereafter, that feature was deleted by Arthur et. al in preparing their Rectified Lunar Atlas and System of Lunar Craters (IAU Transactions XIIB, 1964), and the name was “moved” to the present Cassini (previously honoring G. D. Cassini alone). This is perhaps the first example of a lunar feature name honoring more than one person, a practice that was greatly extended a few years latter and continues to the present day. - JimMosher
  • The IAU’s original “J.” or “J.J.” Cassini is still nicely visible, but now unnamed. - JimMosher
  • According to Ewen A. Whitaker, the secondary crater Cassini E was once known as Felix Chemla Lamèch's Baldet (or... Siredey)(?). The name "Siredey" was not accepted by the I.A.U., the name Baldet is officially located at one of the moon's far-side craters.
  • Another secondary crater, Cassini C, was once known as Zinger. This was another one of Felix Chemla Lamèch's new names, but the I.A.U. officially removed that name to a crater on the moon's far side (known as Tsinger).
  • Research Lamèch's mysterious "Baldet"/"Siredey"-case and "Zinger": Ewen A. Whitaker and Danny Caes (august 2003, mail correspondence).
  • Wilkins and Moore using the 33-inch Meudon refractor on 3 April 1952 claim (page 228) to have discovered within Cassini A "a white, very shallow crater within which is a most minute central pit." They proposed calling this crater within Cassini A "The Washbowl", although the drawing by Wilkins that accompanies the text confusingly gives Cassini A itself the strong appearance of a washbowl with the crater within looking like a drain: the "minute pit" is depicted as a black dot at the center of a shallow circular feature on the eastern floor of the otherwise smooth and much deeper circular bowl of Cassini A. According to Danny Caes, some amateurs continue to use the informal names "The Washbowl" and "The Plughole", but it is unclear if they mean Cassini A and the smaller crater within, or the smaller crater and the still smaller one within it.
    • Wilkins' original report of the "The Washbowl" appears on page 191 of the BAA Journal for April 1955, where the date of the drawing used as an illustration, also claimed to have been made with the 33-inch Meudon refractor, is given as 21 April 1953. The lack of shadow inside the purported crater was noted as a problem at the time this report. Wilkins passed it off as being due to the shallowness of the crater.
    • As Chuck Wood points out, the "The Washbowl" crater within Cassini A does not actually seem to exist. The drawings look very much as if the patch of sunlight striking the ledge on the stepped floor of Cassini A on 3 April 1952 was mistaken for a crater. The slightly lower sun angle expected on 21 April 1953 seems implausibly low for observation of features on the floor of Cassini A. Possibly it is a misprint. - JimMosher

LPOD Articles

A Table of Contents The Cassini Triangle Cassini Observed Cassini North Throwing Out The Washbowl With The Bath Water


  • Drawing and text by Alika Herring. S&T July 1959, p. 515.
  • Hill, Harold. 1991. A Portfolio of Lunar Drawings, pages 14, 15.
  • Lamèch's "Baldet" and "Siredey": Mapping and Naming the Moon; a history of lunar cartography and nomenclature (Ewen A. Whitaker).
  • Launay, Françoise and Willam Sheehan. 2010. "The Mysterious Lady on the Moon." Sky and Telescope Vol. 120 (No. 3, September issue), pp. 26-30.

Dominique and Jacques Cassini in the Sourcebook Project (William R. Corliss)

- In Mysterious Universe, a handbook of astronomical anomalies (1979) :
(articles in which the name Cassini is mentioned)
  • Page 110: Illusions (E.M.Antoniadi, Journal of the British Astronomical Association, 1897).
  • Page 129: Notes on the Rotation Period of Venus (E.M.Antoniadi, Monthly Notices of the Royal Astronomical Society, 1898).
  • Page 137: The Satellite of Venus (T.W.Webb, Nature, 1876).
  • Page 139: The Problematical Satellite of Venus (Observatory, 1884).
  • Page 224: Lights on the Moon (C. Stanley Ogilvy, Popular Astronomy, 1949).
  • Page 357: The Zodiacal Light (Henry Muirhead, Nature, 1888).
  • Page 358: Zodiacal Light Section, Interim Report (P.B.Molesworth, Journal of the British Astronomical Association, 1900).
  • Page 379: The Canals of Mars (E. Walter Maunder, Knowledge, 1894).
  • Page 451: Dark Transit of one of Jupiter's Satellites (Sidereal Messenger, 1884).
  • Page 490: UBV Photometry of Iapetus (R.L.Millis, Icarus, 1973).

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