Repost (Not sure if the listserv is working) At the SLAS star party on Saturday, the lunar asterism the Purbach cross (misidentified by me last night as the Janssen X) was particularly brillantly, illuminated and fully formed lunar "X" near the first quarter terminator when the terminator as at lunar colongitude 359 degs. The following LPOD was taken at first, quarter illumination and shows the lunar X: X Marks the Spot http://www.lpod.org/archive/LPOD-2004-08-29.htm LPOD Lunar X aricle http://the-moon.wikispaces.com/Lunar+X?f=print David Chapman's article on the Lunar X http://idisk.mac.com/chapmandave-Public/WernerX2.pdf This asterism is known by several informal names: the Purbach cross, the Lunar X and the Werner X. Werner is an unrelated fully illuminated crater with the Purbach cross immediately to the lunar northwest - giving the visual impression of an X-O on a tic-tac-toe board. The cross - which looks like an x-chromosone, is formed by the combination of common rim between Purbach, La Caille and Blanchinus. Although the Purbach cross has probably been observed by amateurs since the 1800s, this lunar asterism did not become well-publicized until 2004 by uber-amateur observer Carol Lakomiak. Part of the reason for the lunar x's relative obscurity is for a particular observing point, the Purbach cross is usually observable for only a few hours and then on only alternate lunar cycles or every 59 days. These images on Cloudy Nights nicely show the Purbach cross lunar X as also seen at the SLAS party. The second overlength url (Bill Weir's image) better shows the full "X" also seen at the SLAS star party. Dennis Fell http://www.spacealberta.com/moon/surface/wernerx.jpg Bill Weir http://rascvic.zenfolio.com/p566114947/?photo=h3E47C07F#1044889727 Jane Houston Jones http://photo.whiteoaks.com/2008-04-12-isan/slides/IMG_9833.html The Purbach lunar x is probably second in popularity only to the Hainzel triangle asterism (visible when terminator is near 24-30 deg west lunar long). - Kurt ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ