About the event
On 20 March 2014 UT, the 72 km diameter asteroid (163) Erigone will occult Regulus, a 1.3 mag star in the constellation Leo, for observers along a path across NE USA, E Canada. In the case of an occultation, the combined light of the asteroid and the star will drop by 11.1 mag to 12.4 mag (the magnitude of the asteroid) for at most 14.3 seconds. (source: http://www.asteroidoccultation.com/2014_03/0320_163_32317.htm) Regulus is about 78 light-years away from Earth and the brightest star in Leo and the 21st brightest star in sky. This may be the best and brightest asteroid occultation ever predicted to occur over a populated area. For this reason, many observers from USA and Canada are going to travel to the Lake Ontario to observe this event (see map).
The Club’s expedition
Some brave members of our Club des Astronomes Amateurs de Laval are preparing to travel to the area of the occultation path, near Kingston, ON for this observation. Up to now the occultation commandos are: Gilles Brisson, Yvan Desaulniers, Roger Ménard, Joanne Lafond and Vagelis Tsamis. More observers from the club are welcome!!!
Setup and Observation
On the night of 6/7 March I set up the club’s 8 inch SCT telescope (thanks for lending!) at my home in Laval and took video captures of Regulus and asteroid Erigone, which was at the time 2.5 degrees SE of the target star, two weeks before the predicted occultation. For the test captures I used a Watec 902 H2U video camera and a TIM-10 GPS Video Time Inserter device for accurate timing in each video frame, coupled with a Garmin GPS 18 LVC receiver. An f/3.3 focal reducer was used at the optical path, in order to get brighter images of the 11.9 mag asteroid.
Regulus looked excellent, a very bright star in a star field of dimmer stars:
Asteroid Erigone showed surprisingly well at the live video, although it was at magnitude 11.9 – (but it was … cold) The sky was very good during the observation. I took 3 videos of a few seconds duration each, with a time difference of about half hour. Then I extracted the frames of each video, the frames stacked in MaximDL and made a GIF animation (see 1st picture) in Photoshop. On the second image I raised brightness and contrast values in order to reveal the star field. You can see that faint stars up to magnitude 13.15 were captured (magnitude estimates are rough, they were taken from Starry Night software).
Click on the first image to see the asteroid motion in a GIF
Appendix A: About magnitudes
For scientifically accurate stellar magnitudes one should refer to photometric and astrometric data at astronomical databases like the VizieR Catalogue Service. Newer catalogs like the PPXML and the UCAC4 should be used in most cases. For example, the « 13.15 mag » in the second image above is star UCAC4 0503-053660, which is given a Vmag of 13,452 in the UCAC4 catalog (see the chart at the image below). The magnitude for Erigone was found at Minor Planet Ephemeris Service Center, a website dedicated to solar system minor body astrometry (see table at last image).
Appendix B: Regulus video
Vagelis Tsamis – Club des Astronomes Amateurs de Laval