Occultation by (253) Mathilde this evening in Midwest

Half of Mathilde was imaged by NEAR in 1997; the weather forcast is good for Wisconsin to Kentucky

Help needed with this event to measure the other half of Mathilde

New: 2005 Aug. 23, 16h UT

     This evening (Tues. August 23 local time; Aug. 24 UT), 
11.9-mag. TYC 5687-00325-1 will be occulted by the C-class asteroid  
(253) Mathilde, important since half of this slow-rotating (15d period) 
asteroid was imaged by the NEAR spacecraft during a flyby in 1997.  
Your observations might help determine the dimensions of the 
unobserved (in 1997) half of the asteroid.  The spacecraft 
observations showed that Mathilde is a low-density rubble pile with 
huge craters; some images are on the NEAR Web site.

    The occultation will occur at 2:03 UT (9:03 pm CDT) across 
western and southern Wisconsin; at 2:04 UT across northeastern 
Illinois (including the Chicago area) and northwestern and central 
Indiana (including Indianapolis; an occultation could occur at 
Bloomington); at 2:05 UT (9:05 pm CDT or 10:05 pm EDT) across 
southeastern Indiana and eastern Kentucky (Lexington near the path 
center; an occultation could occur as far northeast as Cincinnati, 
Ohio); at 2:06 UT over northeastern Tenn. (Knoxville), western N. 
Carolina (Charlotte at the northern limit), and northwestern and 
central S. Carolina (Columbia near the s. limit); and at 2:07 UT 
over southeastern S. Carolina.  The Clear Sky Clock forecast is 
clear to mostly clear, with above-average transparency, from the 
Minn./Wisc. border to southeastern Kentucky; from Tennessee to the 
Atlantic coast it is expected to be mostly cloudy.

     Summary information about this occultation was distributed last 
night; this gives more information about this good event.  A central 
occultation is expected to last 9.4 seconds with a 2-magnitude drop.  
The star is a little faint, but should be observable easily with a 
10-inch or larger telescope, and a little marginal with an 8-inch 
telescope.  The star is in Serpens Cauda at J2000 RA 18h 01m 19.1s, 
Dec -14 deg. 18' 07", about halfway between zeta Serpentis and gamma 
Scuti, and almost 5 deg. south of 3rd-mag. nu Ophiuchi.  An 8th-mag. 
star is about 15' west-northwest of the target star.  Star charts of 
different scales and detail are on Steve Preston's Web site,
which also has a map of the path and detailed information.  Very 
detailed maps of the path for this event can be found on 
Charlie Ridgway's interactive Web page that links to the very 
detailed maps and satellite imagery of maps.google.com with overlays 
of the occultation paths. 

A list of stations ordered by distance in km from the predicted 
central line is on Derek Breit's Web site.
Please let us know your plans for observing this occultation so that 
we can optimize coverage of the path - mobile observers don't want 
to duplicate your chord.  So far, the following observers have said 
that they will try to time the occultation: 

Distance
 km from
 center  Observer and location
  +20    Steven Lucy, s.e. Wisconsin
  -22    Steven Messner, Hobbs Obs., Wisconsin

We'd like to add your name and location to this list.
Let me know (at david.dunham@jhuapl.edu) your plans to observe this 
occultation and I will update the list above with your information.
Good luck with YOUR observations of asteroidal occultations.
_______________________________________________________

David Dunham, e-mail dunham@starpower.net, 2005 Aug. 23, 16h UT