Good Occultation by (530) Turandot Fri. am, Feb. 24
This occultation of a star visible in most finder scopes and binoculars is the best in the northeastern USA this winter
The target star is only 3 deg. from Saturn; that and its brightness will make it easy to find
New: 2006 Febuary 20
We need your help to measure the size and shape of the approximately 85-km unusual F-class outer main-belt asteroid 530 Turandot by timing its occultation of 7.9-mag. SAO 80107 (HIP 40832) on Thursday night/Friday morning, February 24, along a path extending from North Carolina to Alberta; some large cities in the predicted path include Raleigh, Cincinnati, Indianapolis, Chicago, Minneapolis, and Regina. The target star should be easy to find, being at high altitude and only 3 degrees west of Saturn in Cancer. This is the best asteroidal occultation in North America this winter; please make a special effort to time it from any convenient location if your sky is clear enough. The star is bright enough that it can be seen with a steadily mounted (held firmly against a fence post or other stable object) pair of binoculars, but a small telescope is recommended if you have one. Use whatever means you have to time the event, with simple methods explained here. We will try to coordinate coverage of the observation; please let me know if you will attempt an observation so that mobile observers can be directed to locations to avoid your line across the asteroid (see station list below). THE PATH The path, which projects to an estimated 113 km wide, is shown on my map on p. 61 of the March issue of Sky and Telescope, but it's better to see the latest updated path on Steve Preston's Web site. Although the new path is almost the same as the one in S&T, Preston's map also shows the 1-sigma limits as dashed lines where it's very possible that the occultation could occur, at locations such as Columbus and Milwaukee; observers within those dashed lines, and a little outside of them (since a path shift greater than 1 sigma is very possible) are also encouraged to try to observe the occultation. The 1-sigma path error is 0.56 path-widths. Very detailed views of the path are at Charlie Ridgway's interactive maps Web site. It has an offset line that you can specify to either iteratively figure out the distance of a given location from the predicted central line in km, or for mobile observers, to find sites at a specified distance from the central line. That site doesn't specify the time, but that can be found from the maps and data on Preston's Web site; the time for a given location estimated from his site should be accurate to about a tenth of a minute. At 7:28 UT (2:28 am EST), the path passes over southeastern & north-central North Carolina, southwestern Virginia, southern and western West Virginia, and eastern Kentucky; at 7:29 UT (2:29 am EST or 1:29 am CST), the path is over northern Kentucky, southwestern Ohio, Indiana from s.e. to n.w., northern Illinois, and southern Wisconsin; at 7:30 UT, n.e. Iowa, w. Wisconsin, Minnesota from s.e. to west-central, & eastern N. Dakota; at 7:31 UT (1:31 am CST), north-central N. Dakota, s.w. corner of Manitoba, and s.e. Saskatchewan; and at 7:32 UT, west-central Sask. and east-central Alberta about 100 km n.e. of Edmonton. The path extends farther northwest across Yukon and northern Alaska. THE STAR AND THE OCCULTATION The spectral type G5 star is at J2000 R.A. 8h 20m 00.1s, Dec. +19 deg. 51' 03", in Cancer 5 deg. west of the Praesepe, 3 deg. west of Saturn, 0.9 deg. south of a 6th-mag. star, and just over half a deg. w.s.w. of a 7.5-mag. star. The target star should be bright enough to see with most finder scopes if it is not too cloudy. A 10th-mag. star 2' northeast of the target star will help confirm its identity. If an occultation occurs, there will be a 7.2-mag. drop to the 15th- mag. of the asteroid (which won't be visible except in large telescopes) lasting 7 seconds for a central event. The observations might reveal the star to be a close double, in which case, the disappearance and/or reappearance will occur in steps. The 19% sunlit waning Moon will be below the horizon for locations along the path at the time and there will be no twilight, with the Sun well below the horizon for the path in North America. Steve Preston's link for this event, giving path maps and detailed finder charts of different scales, is here. STATION LIST AND COORDINATION OF COVERAGE A list of over 200 stations within 3 sigma of the path is at Derek Breit's Web site. From his station list, arranged by distance from the predicted central line, you can see the predicted time of the occultation for your location, as well as the altitudes of the star and Sun, and the probability for an occultation by Turandot. I'll distribute a list of planned sites where observations might be attempted in a few days to help coordinate planning for this good event; by then, a medium-range weather forecast should be available. You can use your Web browser "find" function to find your name or city in the list. If your station is not in the list, send either your coordinates or the postal address of your observing location to me at dunham@starpower.net and to Derek Breit at breit_ideas@hotmail.com With this, you can see the event time and circumstances at your location, and we can know that you'll try the event to help plan our coverage. Let me know if you might be mobile for this occultation, and/or if you might be able to join my planned expedition for it from the DC area. If it is forecast to be clear in North Carolina, I will observe it from sites there near I-95 approximately from Rocky Mount to Fayetteville. I would leave the DC area around noon Thursday February 23 to have lots of time during the evening to set up remote stations. __________________________________________________ David Dunham, IOTA home dunham@starpower.net 301-474-4722 cell 301-526-5590 office david.dunham@jhuapl.edu 240-228-5609