Binoculars Asteroidal Occultations, 2002 Oct. 16, Nov. 3 & 10
Updated: 2002 Nov. 123 binoculars asteroidal occultations, Oct. 16, Nov. 3 & 10, in North America (2 also in Europe) - too bad, poor weather and larger-than-usual path shifts didn't allow us to do nearly as well as the Sept. 17 Tercidina occultation of 43 Tauri, observed from over 70 stations in Europe to become the 2nd best-observed asteroidal occultation - click here to see the detailed profile obtained by these observers, many of whom travelled across national borders to obtain these remarkable observations. Some historical information and brief accounts of the three occultations are given. A simplified beginner's guide to timing occultations is here and some "lessons learned" from the Oct. 27th Alagasta event are here. The predicted paths can be found in the past events (archive) link at Steve Preston's site. Finder charts for these events can be found at the main IOTA site. ____________________________________________________________________ SOME HISTORICAL BACKGROUND September 11 used to be a proud day for American astronomers - 1985 Sep. 11 was the first encounter of a spacecraft with a comet, NASA's ICE mission that flew through the tail of Comet Giacobini- Zinner. And exactly 2 years earlier, at least 33 observers from Virginia to Alabama timed the occultation of 5th-mag. 14 Piscium by (51) Nemausa, at the time the 2nd best observed asteroidal occultation. 1983 will be remembered by asteroid occultation observers for a long time since it was also the year of the top event, of the 4th-mag. spectroscopic binary 1 Vulpeculae by (2) Pallas, timed from 130 stations from Florida to northwestern Mexico. The Nemausa event held the #2 position for 19 years, but on September 17th this year, late Monday night local time, the occultation of 43 Tauri by (345) Tercidina was timed from over 60 stations from Slovakia to France. Dozens of observers crossed national boundaries to observe the event; more Czech observers timed the occultation in the region of Munich than German observers! Details of the numerous observations, including maps showing the distribution of observers and cloudcover, and a reduction profile, are here. The accurate predictions for these events by Steve Preston and Jan Manek, possible now with the Hipparcos-based star catalogs and accurate astrometric observations of asteroids made relative to those data, give us an advantage now for these events; more often than not, mobile observers succeed in timing asteroidal occultations. Unfortunately, many who tried these 3 events as mobile observers in North America did not succede because the paths shifted almost a half path-width north for the Nov. events, and a full path-width south for the narrower Oct. event. ____________________________________________________________________ UT Oct. 16, from UT 4:18 to 4:35, Tues. evening, Oct. 15 in the Pacific Northwest and western Canada. This was the occultation of 4.9-mag. zeta Arietis by Wanghouguan, with a large n. shift from map in March Sky and Telescope. The path passed over n. Libya, Tunisia, n.e. Algeria, central Spain (s. of Madrid), n. Portugal, central Lake Winnipeg, Saskatchewan (n. of Regina), Alberta s. of Calgary, s. Brit. Columbia, and n.w. Washington State (over Seattle). zeta Arietis was the brightest star occulted in North America this year. The occultation lasted about 5 seconds for observers near the central line; the actual path for this small asteroid was about one path-width south of the finally predicted one. Observations in or near the path were attempted only in Iberia, s. Alberta, and Washington. It was cloudy over s. Alberta, and also over most of Iberia, but about six observers in the predicted path near the east coast of Spain (most mobile) had clear skies and no occultation. The occultation was timed from five locations around Seattle, Washington. ____________________________________________________________________ UT Nov. 3, from UT 1:36 to 1:50, Saturday evening, Nov. 2 in North America, the 95-km asteroid (431) Nephele occulted 5.9-mag. Z.C. 593 in Taurus for about 8 seconds along a path well north of that shown on my maps in the March issue of Sky and Telescope. The path started in northwest Russia, passed over southern Finland (several observers tried there, but were clouded out about an hour before the event, except for one observer who was south of the actual path and had no occultation), central Sweden, and southern Norway. It passed over Newfoundland, most of Nova Scotia, most of southern New England (Boston and Hartford were near the southern limit), s. New York (cloudy there), eastern and southern Pennsylvania (Allentown, Harrisburg, Breezewood), w. Maryland, W. Virginia, e. Kentucky, cen. & w. Tennessee (Nashville and Memphis), s. Arkansas, and Texas (Dallas near the central line, but it was cloudy there). A major observing campaign was planned for this good event, but since the path shifted almost a full path-width north, most observers (there were more on the south side of the path) had no occultation. The occultation was observed from about a dozen locations in the northwestern suburbs of Boston, southern New Hampshire, southwestern Pennsylvania, western Maryland, and northern West Virginia. It was cloudy in western Connecticut, New York, and northern and eastern Pennsylvania, and in southwestern West Virginia and virtually the rest of the path southwest from there. Old lists note that the star is a spectroscopic binary, but not the current version of the Bright Star Catalog. The star was not resolved by speckle interferometry, but observers in Japan noted gradual and even step events that they thought indicated duplicity during lunar grazes of the star observed there in 1995 and 2001. But examination of the video records obtained during the Nephele occulation seem to show only rather quick disappearances and reappearances consistent with Fresnel diffraction; the star seems to be single. A central occultation was expected to last about 8 seconds with a 7-mag. drop, but I think the longest durations reported so far are under 7 seconds. Richard Nugent, who travelled to Maryland from Houston for the event, observed from a location 6 km south of the predicted southern limit south of Cumberland and video recorded an occultation that lasted only 1.5 seconds. The Naylor Observatory of the Astronomical Society of Harrisburg, at Lewisbury, Pennsylvania, was only 2 km farther south relative to the path and they video recorded no occultation there, as did many other observers, including myself, at locations a few to many miles farther south. Pre-event messages and data can be found here (Oct. 24), here (Oct. 28), and here (Oct. 29) for observing the event. ____________________________________________________________________ Unfortunately, almost all observers of the Lindemannia occultation were clouded out, especially most of the over 80 observers, most of them mobile, that Paul Maley recruited to cover the predicted path at better than 1-km resolution; there was a flow of humid air from the south that condensed into clouds and fog over most of eastern Texas during the hours (and in some cases, the minutes) before the occultation, and conditions were worse east of there. It stayed clear around San Antonio (which had no occultation due to the north shift of the path) and Austin (which had an occultation, although it was just north of the predicted northern limit), so observers from those cities were successful (the ones in the actual path), and a few Houston-area observers also travelled far enough north or west to see the occultation - a brief early summary is here. The prediction information for this event is given below. UT Nov. 10, from UT 6:28 to 6:36, early Sunday morning in USA, the 53-km asteroid (828) Lindemannia will occult 5.3-mag. pi Arietis at J2000 RA 2h 49m 17.6s, Dec +17 deg. 27' 51" for about 4 seconds along a path again well north of that shown on my maps in the March issue of Sky and Telescope. The path starts in the Canary Islands, then makes landfall at Charleston, S. Carolina; passes over southern Georgia, Alabama (just n. of Mobile), Mississippi, and Louisiana (just s. of Baton Rouge); across southern Texas (just north of Houston and over Austin/San Antonio); and across n.w. Mexico. Paul Maley, pdmaley@yahoo.com, and Rick Frankenberger, rickf@stic.net, have mobilized many dozens of observers around Houston and San Antonio, respectively; click here for very detailed maps, observing information, and station lists. Paul Maley has set up a good Web page about the event. and Steve Preston, working with Paul, has a map showing the nominal path in detail across the Houston, Texas region with prospective observer locations indicated with red dots and coverage lines at 1-mile intervals; see the link above. The maximum duration will be about 4 seconds with a 9-mag. drop. ____________________________________________________________________ David Dunham, IOTA