Asteroid 773 Irmintraud occults UCAC2 12089544 in Ara

This is my first successful stellar occultation event. As the asteroid passes in front of the star, it hides the star completely, so that only the light from the asteroid remains. Because the shadow of the asteroid is passing us very fast (10.1 kilometers/second), the stars light drops in an instant and pops back just as fast.

The animation shows the star wink out and back in an instant. With the GSTAR-EX video camera set at x0 sense up (25 frames per second), it yields the greatest timing resolution at +-20 milliseconds for each interlaced video half-frame. Using a diffraction curve analysis in LiMovie software, the time can be refined even further.

The light graph below was generated in Limovie and shows the magnitude drop from the star (11.0 magnitude) and asteroid to the asteroid alone (13.0 magnitude). The blue lines and points are the star being occulted and the yellow points are of a nearby comparison star.