Tuesday night, 2007 April 17 (EDT), Iota Cancri A dimmed out as expected when asteroid 411 Xanthe passed over this fourth magnitude, double star. Despite potential clouds and haze that would have ruined seeing this exciting event, most people who tried to time the occultation had remarkable success. Even if you did not attempt to time this occultation, hopefully some of you observed this dramatic event when this yellowish star winked out leaving its fainter bluish companion behind! (It may not seem thrilling to watch a star go out for several seconds, but ask someone has seen this and they will tell you otherwise!) Thanks to all dedicated observers, especially those AAC members who had never seriously observed an asteroid occultation before. You should all be gratified with your success. Your data will help astronomers improve our knowledge of asteroids. AAC member Don Loftus has already posted an MPEG-4 video clip on YouTube: http://www.youtube.com/watch?v=iiC28i3v44U (The image jiggles because Don handheld the video camera to his telescope eyepiece.) Other videos will likely follow and the AAC will probably have a program later this year at a monthly meeting to discuss and show results. Some preliminary results from various observers who reported approximate durations are listed below. Some comments by David Dunham (Contributing Ed., "Sky & Telescope") are listed after the results. Note: Dunham has also posted a preliminary summary on his web site at: http://iota.jhuapl.edu/mp411.htm ----------------------------------------------------------------------- SOME PRELIMINARY RESULTS [PCL = predicted center line; approximate path width = 76 km] David Dunham (Deltona): abt. 65 km. S. of PCL, no occultation. Note: David was abt. 25 km S. of the path limit and would have only seen an occultation if the path had moved south. Scott McCartney (Gainesville): abt. 36 km S. of PCL; no occultation! Note: Scott was abt. 2 km within the path and should have seen a brief disappearance but did not! Don Loftus (N. of Gainesville): abt. 22 km S. of PCL, abt. 2 sec. Richard Nugent (near Ormand Beach): abt. 20 km S. of PCL, abt. 2 sec. Chuck Broward/Bob O'Connell (near Keystone Hts): abt. 13 km S. of PCL, 6 sec. Bill Helms (Live Oak): abt. 1.4 km S. of PCL, abt. 8 sec. Tandy Carter (SW of Lake City): abt. 0.5 km S. of PCL, technical difficulties and missed the occultation. Francisco Reyes (E. of Live Oak): abt. 5 km N. of PCL, abt. 8 sec. Howard & Marian Cohen/Larry Friedberg (NE of Live Oak): abt. 9 km N. of PCL, abt. 8.5 sec. Paul Maley, Pablo Vasquez (Osceola Nat'l Forest): abt. 30 km N. of PCL, abt. 8 sec. Mike Toomey (Osceola Nat'l Forest): abt. 30 km N. of PCL, abt. 8 sec. Kyle Culpepper, Martha Leake (Valdosta, GA): abt. 40 km N. of PCL, abt. 6 sec. Note: Valdosta is about 4 km N. of the northern limit and should not have seen the occultation but did! --------------------------------------------------------------------------- Dunham says preliminary results suggest the actual path may have been about 20 km farther north than expected. He also writes that our data should ultimately allow one to determine the shape of Xanthe quite well. In addition, the occultation data should also help determine the star's angular diameter. Dunham also reports the occultation appears to have arrived about 12 seconds earlier than predicted. (My own observations had the occultation about 15 seconds early.) Some observers reported a slight delay during the disappearance and possibly a slight delay reappearing. Dunham says this was probably due to Fresnel diffraction of the star's light at the edge of the asteroid (a phenomenon due to the wave nature of light), probably enhanced by the star's angular diameter. Howard Cohen AAC Vice President Assoc. Professor Emeritus, Univ. of Florida 2007 April 18