TITANIA HIDES A BRIGHT STAR On Friday night, September 7-8, 2001, the largest moon of Uranus, Titania, passed almost directly in front of a 7.2-magnitude star (HIP 106829). For observers in a wide path that sweeps from western Europe to the northern tip of South America, the star disapeared for up to 76 seconds. Nothing quite like this has occurred since July 3, 1989, when Saturn's largest moon, Titan, covered 28 Sagittarii in an even rarer occultation. The occultation was visible in Venezuela, Colombia, Panama, Ecuador, and northernmost Peru, where Uranus and its moons were high in a fully dark sky. Conditions were also favorable in extreme southwestern Europe, where the event took place near 1:55 UT, well before the start of Saturday morning twilight. Click on image for full-sized view. Titania occultation map (Sky and Telescope) "This event has special value since Titania, like Neptune's moon Triton, may have a thin atmosphere," comments David W. Dunham, president of the International Occultation Timing Association (lOTA). "Plausible models show that the dimming due to such an atmosphere should be easy to detect, if it exists, with video, CCD, and photoelectric recorders." Titania occults HIP 106829 Preliminary results Location: Observatory Fernando Tonel, Portugal 37 Deg 08 min 28.7 sec N 8 Deg 37 min 33.2 sec W, Elevation: 64 m Observers: Fernando Tonel, Pedro Ré, Helmut Denzau Telescope: 10 inch SCT, f=2540 mm Detector: IOTA Occultation Camera, TC 245 Chip, 50X50 pixel window Sampling 0.22 s, Binning 3, 12 bit dynamic, no Filter Timing: DCF 77 Recording time: 1 h 30 min - 2 h 25 min UTC Beginning of occultation: 1 h 54 m 45.2 s UTC End of occultation: 1 h 55 m 27.7 s UTC Duration of occultation: 42.5 s +- 0.13 s Fading of the star about 0.5 s Click on images for full-sized view. Meade LX200 10 inch SCT, f=2540 mm. IOTA Occultation Camera, TC 245 Chip, 50X50 pixel window Sampling 0.22 s, Binning 3, 12 bit dynamic, no Filter Dr. Helmut Denzau (IOTA) + Telescope and detector Laptop controlling IOTA Occultation Camera Occultation data Preliminary results (Portugal)