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First Occultation with OmegaCass

Last modified on November 17, 1998 by A. Richichi

An occultation of the late-type star SAO 95190 was recorded at the Calar Alto Observatory's 3.5m telescope using for the first time the Omega-Cass camera. This uses a 1024 x 1024 pixel HgCdTe array (HAWAII), which can be read-out at fast speed in a subarray. A similar mode existed for 256^2 PICNIC detectors, and was used to carry out lunar occultations with the MAGIC and ARNICA instruments. This is however to our knowledge the first use of a HAWAII detector for similar work.

The occultation reappearance of SAO 95190 was recorded on October 11, 1998 by T. Herbst and Ch. Leinert. A movie is available (300Kb), showing a sequence of about 2.4 seconds in a 32 x 32 pixels subarray, corresponding to 9.6 x 9.6 arcseconds on the sky. The data were obtained at 2.2 microns with 4 milliseconds integration time and a frame rate of 125Hz. A preliminary analysis of the data shows that the source is unresolved, with an upper limit of 0.0016 arcseconds on the angular diameter (as expected for this G5, V=8.2 star). The SNR in this preliminary analysis (no flat-fielding included yet) shows that occultations at the 3.5m with Omega-Cass have the potential to reach K=12 mag or fainter.

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