Large Asteroid (790) Pretoria Occ'n Oct. 29 am, BC to MS
Updated: 2005 Oct. 28
2009 October 29, 5:59 am CDT (10:59 UT): Occultation of 10.8-mag. TYC 0216-01594-1 by the 170-km asteroid (790) Pretoria, visible from a path passing over Tulsa, OK, about 100 miles northeast of Stillwater. ________________________________ Here was a plan to cover Saturday morning's (790) Pretoria occultation path; distances are in km from Steve Preston's central line, + for distances northeast, and - for distances southwest: Dist., km +85 David Dunham attended station +65 David Dunham remote station +45 Bob Sandy +27 Chad Ellington +9 Benny Roberts, Jackson, MS -5 Roger Venable attended station -20 Paul Maley -30 Derald Nye near Tulsa -40 Richard Nugent -60 Derek Breit with Roger Venable's 2nd station -80 Rick Frankenberger -109 Art Lucas at his observatory You can see the path superimposed on very detailed maps and satellite imagery on Charlie Ridgway's Web site. For general information about his site, click here, while for the map specifically for the Pretoria occultation, click here. On this site, you can enter a distance from the central line in km in a special "offset" box (just write over the default value of 1000 given there) and it will plot gray lines at that distance north and south of the central line. Type your distance number (in km) in the box just to the left of the "Plot Offsets" box at the bottom of the map. You need to type a number with no sign, then two gray lines are plotted; zoom in on the gray line northeast of the yellow central line if your distance is + and on the gray line southwest of the central line if your distance is -. You can move the map by grabbing it (left-clicking and holding down) and you can zoom in or out by left-clicking on the scale in the upper left part of the map (+ on that scale means "zoom in" for more detail over a smaller area). You can toggle between "map" (showing town and road names), "satellite" for satellite imagery, and "hybrid" for both together. Derek Breit's Web site shows that for Tulsa, and locations along I-44 across the path, the occultation will occur at 10:58.8 UT (5:58.8 am CDT) and will occur 0.1 min. later, 5:59.0, where the central line crosses the western Arkansas border. Observers in Oklahoma should observe/record from 5:57 to 6:01 am CDT (10:57 to 11:01 UT) at least. The Clear Sky Clock 23h prognosis charts, for 11h UT of Oct. 29, shows a now smaller patch of clouds over north-central Oklahoma and s.e.Kansas that, if it develops as forecast, will cause problems in Wichita and maybe Stillwater, but probably not Tulsa nor along I-44. It is predicted to be quite clear from the Tulsa area to the Gulf coast of Mississippi and Alabama. Some observers in Washington State and British Columbia plan to try to observe the occultation, but lots of clouds are expected there, and in most places in the path northwest of Tulsa, Oklahoma. Another forecast update will become available just after noon EDT, and I will post any change to this forecast on my Web site at http://iota.jhuapl.edu/mp790.htm by about 1 pm EDT = 17h UT, but I will not be able to distribute an e- mail message about it to most of you then. _______________________________________________________ We need your help to observe the occultation of 10.8-mag. TYC 0216-01594-1 by the 170-km asteroid (790) Pretoria, visible from a path passing over Tulsa, OK, about 100 miles northeast of Stillwater. The path also extends from southern British Columbia to Key West, Florida (but twilight becomes a problem there, not to mention flooding from Wilma); see below for a description of the path. If an occultation occurs, there will be a 4-mag. drop lasting up to about 9 seconds. For more information about this event, see Steve Preston's Web site that now includes some fairly detailed maps of the path and detailed finder charts of different scales to easily locate the star. After this occultation, the 2005 annual meeting of the International Occultation Timing Association (IOTA) will be held in Stillwater, Oklahoma; arrangments have been made to Webcast the meeting. The IOTA meeting will start 4 hours after the Pretoria occultation, at 10 am CDT (15h UT); for details about it, click here. If you can help us observe this occultation, either from your home or observatory, or as a mobile observer, please inform me and Derek Breit (e-mail breit_ideas@hotmail.com ). For coordinating coverage of this occultation, a list of stations sorted by distance in km from the predicted central line, can be found on Derek Breit's Web site. You can search for your, or your town's or observatory's, name to see just when the occultation is predicted for your area (that time should be accurate to within 15 seconds or so), the probability for having an occultation there, and the predicted Sun and star altitudes at the time. If your station is not in the list, send me and/or Derek Breit your coordinates, or your street address, and we can add it. Derek will update his Web site with information indicating which distances from the central line (or "chords") will have observers trying to time the occultation. For information about timing occultations, click here. At 10:57 UT (3:57 am PDT), the path passes over southwestern British Columbia (Vancouver just inside the s. limit), northern Washington State (Spokane is near the center), northern Idaho, & s.w. Montana. At 10:58 UT (4:58 am MDT), the path crosses Wyoming diagonally from n.w. to s.e. (both Yellowstone and Laramie are near the s. limit), s.w. Nebraska, n.e. Colorado, Kansas from n.w. to s.-center, Wichita near the center), and n.e. Oklahoma (Tulsa just s. of center). At 10:59 UT (5:59 am CDT), the path crosses western and southern Arkansas, n.e. Louisiana, southern Mississippi, and s. Alabama (Mobile is inside the n. limit). You can see the path superimposed on very detailed maps and satellite imagery on Charlie Ridgway's Web site. For general information about his site, click here, while for the map specifically for the Pretoria occultation, click here. On this site, you can enter a distance from the central line in km in a special "offset" box (just write over the default value of 1000 given there) and it will plot gray lines at that distance north and south of the central line. The target star should be easy to locate, at J2000 RA 8h 47m 12.3s, Dec +2 deg. 09' 18", just south of the distinctive pattern of stars that form Hydra's head south of Cancer. The target star is only 1.6 deg. southeast of 5th-mag. eta Hydrae (the s.e. star of Hydra's head), 0.5 deg. southwest of a 6.5-mag. double star, 23' s.s.e. of an 8.5-mag. star, and 8' west and a little north of a 9.5-mag. star. The medium-range weather forecast is good for Oklahoma, with only scattered cirrus forecast. I have not yet checked the forecast for other areas along the path; more details about the weather forecast will be available soon.