Occultation by asteroid 329 Svea

Observed: 7 Nov 2007

Michel Bonnardeau
9 Nov 2007
updated 30 Nov 2007
revised 28 Dec 2007 (GPS time uncertainty)
corrected 10 Apr 2017 (shadow size)

Abstract

The minor planet 329 Svea was observed occulting a 11.54 mag star. The duration of the occultation was 7.7±0.2s.

Observation

The occultation of mag 11.54 star 2UCAC31985164 (GSC115-01328) by the asteroid 329 Svea on 8 Nov 2007 UT in the vicinity of my location was predicted by S. Preston: http://www.asteroidoccultation.com/2007_11/1108_329_9159.htm.

The observation was carried out with a 203mm f/6.3 SC telescope, a Clear filter and a SBIG ST7E camera (KAF401E CCD). The exposure was 60s long, starting at 00:33:28 TU: I let the telescope tracks for about 10s, then I switched off the RA drive.

I estimate the uncertainty on the time with my NMEA GPS as 2s (I compared with the French Horloge Parlante 3699). Futhermore, MaximDL3 records the time to the nearest second. The total uncertainty on the timing of the beginning of the occultation is then +/-2.5s.

A part of the resulting image is:


1: the occulted star at the beginning of the exposure;
2: the beginning of the occultation;
3: its end;
4: the occulted star at the end of exposure.

I solved the astrometry of the image: The image is 0.2937° and 765 pixels width. The angular distance between 2 and 4 is 4.26'+/-2pixels or 17.0+/-0.2s, then the beginning of the occultation 2 is at 0:34:11 TU +/- 2.7s. The angular distance between 2 and 3 is 1.93'+/-2pixels and the duration of the occultation is 7.7+/-0.2s.

Another analysis is to rotate the image so that the trails are parallel to the X axis; this was done with MaximDL 4.60, the rotation being 1.36°. The intensity profile of the trail with the occultation can then be extracted:



The average intensity during the occultation is 211.5+/-3.1 where the uncertainty is the standard deviation, for the trail it is 228.8+/-3.4, and after the trail (the image background) the intensity is 211.7+/-2.9. The lengths are measured at mid-heights (I checked that a 60s exposure with MaximDL does give a trail of 653pixels). The distance between 2 and 4 is then 188.0+/-1.6pixels or 17.32+/-0.15s, yielding the time at the beginning of the occultation of 00:34:10.68+/-2.65UT. And the occulation duration is 83.75+/-0.55pixel or 7.72+/-0.05s.

Technical notes

Telescope and camera configuration.

Computer and software configuration.