----- Original Message ----- From: David Dunham To: planoccult@aula.com Sent: 11 May 2007, 04:26:52 UT Subject: [PLANOCCULT] Possible occultations by rings of Pluto tomorrow night, & July 31 & Sept. 27 At about 4.7h UT of May 12 UT, Pluto will occult 13.3-mag. UCAC2 25822467, at J2000 RA 17h 53m 32.0s, Dec -16 deg. 22' 47", in a path passing over much of Antarctica and Patagonia. But in addition, Walker Vaning believes that rings of very small particles will also occult the star for observers in the whole hemisphere facing Pluto, which includes all of South and Central America, most of the Atlantic Ocean (including the Canary Islands), the Caribbean Sea, eastern Mexico, eastern USA, and eastern Canada. Vaning thinks that occultations by the rings could occur even a few hours from the closest approach time, so that observers in western Europe & southern Africa might try to record before sunrise, and those in western North America have a chance as soon as Pluto rises high enough for effective observation. Since the particles are small, there is a substantial wavelength dependence on the visibility; Vaning recommends observing in the blue, at as short a wavelength as possible. Vaning claims that he finds as many as 30 rings in the KAO blue observations of the 1988 occultation, but that the ring occultations are very shallow or absent in visual and red wavelengths. David Herald predicts two more occultations of reasonably bright stars this year, of 13.3-mag. UCAC2 25815762 at J2000 RA 17h 45m 42.0s, Dec -16 deg. 29' 32", visible from much of Antarctica and probably New Zealand (the latter especially considering the north shift from Pluto's ephemeris that may have caused the north shift during the March occultation) on July 31 around 13.8 UT, with ring occultations possible also as seen from Australia, Indonesia, Philippines, Japan, Asia, and eastern Africa. Then on Sept. 27, around 14.8 UT, the Earth will pass between the shadows of Pluto and Charon, with no occultation by either object visible from Earth's surface, involving the 8.7-mag. (!) star SAO 160793 = UCAC2 17h 44m 38.4s, Dec. -16 deg. 46' 35"; the night area of possible occultations by Plutonian rings being most of Asia (from Arabia to Vietnam to western & southern China to the Ural Mountains, the Horn of Africa, western Australia, part of Antarctica, and the Indian Ocean. David