Station Map for the Occultation by (227) Philosophia at Saturday, 2009 May 02 (~ 19:39 – 20:32  UT)

Magnitude of target star 2UCAC 30701154: 12.9 mag
Combined magnitude of star and asteroid: 12.3 mag

The max duration is expected to be 297.8 sec with a max drop of 0.9 mag only. (See notes below)
The event will take place at an altitude of 38 deg and at azimuth 189 deg. The sun will be at an altitude of -14 deg. (At predicted centre line for longitude E 10 deg)

Comments about this unusual SLOW-MOVING event at PLANOCCULT:

Dave Herald, Australia:
„… the Philosophia event next May 2 is a very practical an exciting event. With a potential duration of 5 minutes (yes – 5 MINUTES), a timing resolution of 0.1 secs will equate to a resolution at the asteroid of 30 meters! Note that because of the slow motion, the prediction uncertainty is about 6 minutes in time  Hopefully there will be a major effort by the Europeans to observe this event…!“

Jean Lecacheux, France:
„Over Europe the shadow of PHILOSOPHIA will move to the opposite of Earth rotation, and so the occultation will be appreciably shorter that the theoretical 5 minutes of a virtual geocentric event.
So I calculated the precise duration in Strasbourg, the large city at the border between Germany and France (where the occultation should happen near the end of nautical twilight), and found 2.5 minutes
This is an exceptional occultation slowness nevertheless, as the shadow will progress by only 11.7 meters during a video frame!“

There is a 1 sigma uncertainty interval of  ± 1.31 path widths.
Jean Lecacheux about slow moving asteroids and calculated probabilities at PLANOCCULT:
„For a lot of reasons slow events appear (and are) especially interesting, but please keep suspicious about their possibly overestimated probability.“

The probabilities to see a positive event (very uncertain):

Centre line: ~  30 %
Path limits: ~  28 %
1 sigma lines:  ~ 12 %
2 sigma lines: ~ 1 %

(Calculation according to Raymond Dusser, E.A.O.N. Circular #10)

PLEASE REMEMBER: Predictions are sometimes wrong. Please observe even with a small probability.
Let other observers know about you observing plans: Announce you station with OccultWatcher !

More information (coordinates, finder charts) at Steve Preston’s prediction:

Table of potential observing stations and cities with distance from center of predicted path (Derek C. Breit):

Map and Coordinates at the web page of  E.A.O.N.:

Good luck with your observation!

Oliver Klös


(227) Philosophia, 2009 May 02, Station Map

Leave a Reply

You must be logged in to post a comment.