Asteroid (99) Dike Occultation Dec. 1 am, Delmarva to Mongolia
Hundreds of telescopes are in this path, also over Washington, Pittsburgh, Cleveland, and Detroit
Accuweather indicates conditions may be good in the Maryland - n. VA - DC region, but poor towards the northwest
The 8.9-mag. star is in a rich Milky Way field in Auriga
New: 2005 Nov. 28
Accuweather forecasts about 40% cirrus in the Washington, DC region, so chances look good for being able to see this relatively bright star over 40 deg. above the northwestern horizon in our area. Chances are poorer for areas northwest of our region. If you have a 2-inch or larger telescope, we need your help to observe the occultation of 8.9-mag. SAO 58354 = HIP 26902 by the 69-km asteroid (99) Dike, visible Thursday morning Dec. 1st in a path passing over the southern Delmarva Peninsula, southern and western Maryland, northern Virginia, and Washington, DC at 10:15 UT = 5:15 am EST Nov. 11; at 10:16 UT over n.e. West Virginia, south- central & western Penn. (Pittsburgh at s. limit, Erie and Harrisburg north of the northern limit but within the 1-sigma uncertainty zone where an occultation is possible); n.e. Ohio, s.w. Ontario, and eastern and northern Michigan (Detroit just s. of the s. limit); at 10:17 UT (4:17 am CST), over western Upper Michigan, extreme n.e. Minnesota, western Ontario, and eastern Manitoba n.e. of Winnipeg; then the path extends across n.w. Canada, northern Alaska, eastern Siberia, n.e. China, and s.e. Mongolia (10:26 UT), rather forbidding lands with no known occultation observers. For more information about this event, see Steve Preston's Web site. It has detailed finder charts of different scales to easily locate the star. Guy Nason has prepared some quite detailed maps of the path from eastern Manitoba to the Atlantic: Maryland, e. & n. Virginia, n.e. W.Va. Pennsylvania & n.e. Ohio Michigan & n.e. Minn. w. Ontario & e. Manitoba Power Point file with all four maps. 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, are 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 with some more good information by Guy Nason here. Let me know your plans, whether you plan to observe from a fixed site or are mobile, needing a line to aim for. During the next nights, I'll distribute an edited down list of stations from Derek Breit's more extensive list including only those who have said that they will try to observe this good event. I hope to try to observe the occultation from multiple sites across the path, probably mostly near US 301 from s. of Bowie to the Nice Bridge, but may select a different area, depending on the weather. If any others in Maryland or DC-region want to help me with this, let me know. Guy Nason also is organizing observers in southwestern Ontario; for details, including a more detailed map of that area, click here. 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 Dike 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. The target star is 3.4 deg. west-southwest of 3rd-mag. theta Aurigae at J2000 RA 5h 42m 41.5s, Dec +36 deg. 08' 59"; the target star is two deg. southwest of 5th-mag. upsilon Aurigae and only 5' southeast of an 8th-mag. star, and 30' north and a little east of a 7th-mag. star; there's a distinctive pattern of other 9th-mag. stars near the target star in this rich winter Milky Way field that will help locate the target. The spectral class of the target star is B5. If an occultation occurrs, it would last up to 5 seconds with a 5- magnitude drop. There are other occultations soon in the Mid-Atlantic region, but this is the best asteroidal occultation passing over the Washington, DC area this year, so it deserves a special effort. If the weather forecast remains good enough, plan to go to bed a little earlier than usual Wed. night so you can get up a little earlier to try this good event. David Dunham e-mail home dunham@starpower.net; office david.dunham@jhuapl.edu