MBCAA Observatory

Occultation by 131 Vala

Observed: 8 Apr 2017

Michel Bonnardeau
10 Apr 2017, updated 6 Jun 2017


The minor planet 131 Vala was observed to occult star TYC 6185-00247-1 on 2017 Apr 8. The occultation duration was 8.9140.069s.


The occultation of the 10.9 mag star TYC 6185-00247-1 by the 13.4 mag asteroid 131 Vala on Apr 8, 2017 was predicted on Steve Preston's Predictions Website. The details of the prediction are here.


The observation was carried out with a Meade LX200 203mm f/6.3 Schmidt-Cassegrain telescope, a Clear fiter and a SBIG ST7E camera (KAF401E CCD). A few seconds before the occultation, the equatorial motor is shut down and the camera obturator is opened and 60 seconds after the begin of the exposure the obturator is closed. The time is recorded using a Garmin GPS 1PPS device connected to the computer RS232 port and the TAC32 software program.

The resulting image show star trails with an interruption due to the asteroid.

The trace begin is at 02:58:58.117 ± 0.044 UT
the ingress at 02:59:27.734 ± 0.088 UT
the egress at 02:59: 36.647 ± 0.092 UT
the end at 02:59:58.117.
The duration of the occultation is 8.914 ± 0.069 s. It is slightly larger than the predicted maximum duration of 8.7 s.

Based on the orbital period of 1385.669 d (3.79 yr), the fact that the orbit is nearly circular, the geocentric distance of 1.389 AU, the velocity of the asteroid's shadow at Earth location is 10.9 km/s. The speed of asteroid's shadow on Earth surface (taking into account its motion) is given on S. Preston's website as 3.7392 km/s. The dimension of the shadow that flied over my location was then 33.3 km.

A report was sent to Planoccult (may not be available on line). Unfortunatly, no one else observed this occultation.

Technical notes

Occultation timing. (may not be available on line)

Telescope and camera configuration.

Computer and software configuration.

Data processing.

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