From IAU Circular #7320
updated 7 Dec. 1999

On Nov. 19 D. W. Dunham, Applied Physics Laboratory, Johns Hopkins University, reported the visual observation by B. Cudnik (Houston, TX, 0.36-m telescope) on Nov. 18 of a brief flash near the center of the moon's dark limb, at least as bright as psi1 Aqr nearby. This event, 1'.7 from the moon's edge, was apparently confirmed by Dunham (Mount Airy, MD, 0.13-m telescope) on two half-frames of a videotape that showed fading by about 5 mag during the intervening 1/60 second. On Nov. 23 and 24 Dunham reported his confirmation of two lunar flashes videorecorded by P. V. Sada (Monterrey, Mexico, 0.13-m telescope) half an hour after Cudnik's observation, as well as of two lunar flashes videorecorded by D. Palmer (Greenbelt, MD) up to an hour or so earlier; there was also a probable untimed additional visual confirmation of the Cudnik event by S. Hendrix (Cameron, MO, 0.11-m telescope). Dunham has summarized his own measurements of the five Nov. 18 events as follows:

             +/-          Discovered  
Name  U.T.    sec.   m1 m2    by       lambda beta Lunar Location
   h  m   s                              deg. deg.
D  3:49:40.5   0.4   3  7  David Palmer  48W   1N  175km SW of Kepler
E  4:08:04.1   0.6   5  8  David Palmer  70W  15S  175km S of Grimaldi
A  4:46:15.2   0.1   3  8  Brian Cudnik  71W  14N   50km ENE of Cardanus
B  5:14:12.93  0.05  7  8  Pedro Sada    58W  15N  200km WNW of Marius
C  5:15:20.23  0.05  4  7  Pedro Sada    59W  21N   75km S Schiaparelli 

The magnitude m1 is that on the first video frame showing the event, m2 that on the following half-frame; the first event listed also seems to be present on third half-frame at mag 9. The selenographic coordinates (longitude lambda and latitude beta) and lunar location for the first two events are uncertain by 5 deg or more, but the others should be accurate to within about 2 deg (50 km). Following Dunham's suggestion that the flashes resulted from Leonid impacts on the moon, D. J. Asher, Armagh Observatory, computed that the center of the 1899 dust trail that evidently produced the 1999 Nov. 18 Leonid activity (cf. IAUC 7311) by nominally passing 0.0007 AU from the geocenter would have passed 0.0002 AU from the selenocenter around 4h49m UT.