[BAA 00354] Favourable asteroid occultation on Wednesday night, 24th Sept

[Rick]

BAA electronic bulletin No. 00354 -- http://www.britastro.org/

On Wednesday night, 2008 September 24, at around 2237 UT (2337 BST), the 113km asteroid (56) Melete is predicted to occult 11th magnitude star TYC 0633-01047-1 in the constellation Aries.

The latest update (Sept 17) shows the shadow track crossing north-east, central, and central-southern England, with most of the rest of England being within the uncertainty zone.  The star will be at an elevation of about 33º, in azimuth 119º (ESE).  The sun and moon will be well below the horizon.  The maximum duration, on the centre line, will be a 'whopping' 13.6 seconds, with a 1.3 magnitude light drop.

As with all asteroid occultation predictions, there is some uncertainty in the precise location of the track.  Taking into account the formal errors, the probability of observing a positive event in this case is around 50% within the shadow track (over 90% near the centre line).  The predicted centre line passes over or close to Grimsby, Boston, Peterborough, Northampton, Bedford, Milton Keynes, High Wycombe, Reading, Woking, and Southampton.  But many other major cities, including London, are within the wide track.

To see the detailed track, click on the link below to display Derek Breit's high precision plot of the event on a Google Map, and zoom in to the UK:-

http://www.poyntsource.com/New/Google/20080924_13146.HTM

The predicted centre line is shown in green, the shadow track edges in blue, and the 1 standard deviation track in red.  (Ignore the movable grey lines.)  More detailed information about the occultation and maps are here:-

http://asteroidoccultation.com/2008_09/0924_56_13146.htm

Good 'Planetarium Software' can assist in identification of the correct star.

Scientifically valuable information can be obtained from accurate timings of the disappearance *and* reappearance of occulted stars. A single positive timing can yield a much higher precision position of the asteroid relative to the star than standard astrometry. Combined timings from observers distributed across the track can yield the size and shape of the asteroid.

Observers wishing to make serious visual timings (to better than 1 second) will need a multi-lap stopwatch or a voice recorder linked to an accurate time signal.  Those with a sensitive enough video camera and telescope combination may also be able to record the events, but will need an accurate method of time-stamping the video.  CCD video cameras have extended sensitivity into the red and IR: The star's red magnitude is 10.7

Serious timings of positive occultations would be welcomed by the undersigned, as would definite negative events from within the predicted shadow track.  It is normal practice to observe or record for 2 minutes either side of the predicted central occultation time above.  A specimen report form can be found at:-

http://astrosurf.com/eaon/Report%20form.htm

Please email any reports to me, or contact me if you need assistance completing the form.  Accurate latitude and longitude (WGS84 datum) can be obtained from the Google Map, before or after the event.  Elevation above MSL is also required.

Good luck!

Andrew Elliott

Assistant Director (Occultations), Asteroids and Remote Planets Section