MBCAA Observatory

Occultation by asteroid (429) Lotis

Observed: 8 Aug 2010

Michel Bonnardeau
9 Aug 2010
updated 24 Sept 2010 (astronomical note), 24 Aug 2012
corrected 10 Apr 2017 (shadow size)


The minor planet 429 Lotis was observed occulting a 11.3 mag star. The duration of the occultation is 1.8±0.4s.


The occultation of the 11.3 mag star UCAC2 31 081 100 by asteroid (429) Lotis on 8 Aug 2010 was predicted by S. Preston and the information conveyed over the Planoccult mailing list.

The observation was carried out with a 203mm f/6.3 SC telescope, a Clear filter and a SBIG ST7E camera (KAF401E CCD). The conditions were fairly good. The exposure was 60s long, starting at 23:06:50 UT: the telescope tracked for 5s, then the drive was switched off by computer. The stars then trailed for 55 s.

The computer clock was checked by listening to the Horloge Parlante (Observatoire de Paris, France) and its precision is estimated to +/-0.5s. Futhermore, the program for the image aquisition (MaximDL V4) records the time to the nearest second.

A part of the resulting image is:

1: begin of the trail
2: begin of the disappearance
3: end of the disappearance
4: end of the trail.

My image is 0.294 and 765 pixels width. The trails are 607+/-1 pixels long, start at 23:06:55 UT and lasts 55 s. The distance between 1 and 2 is 272+/-1.5 pixels, and between 2 and 4 335+/-2.5 pixels. The disappearance is then at 23:16:19.6 UT +/-1.3s. The duration of the occultation is 19.5+/-4.0 pixels or 1.8+/-0.4s.

Astronomical note

The occultation was also observed by C. Gualdoni, in Italy. A computation of the chords by Euraster is HERE.

Technical notes

Telescope and camera configuration.

Computer and software configuration.

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