Comet Wirtanen near Aphelion

This is a reproduction of a photo based on the addition of twelve images of the nucleus of Comet Wirtanen near aphelion, obtained with VLT KUEYEN and the VLT Test Camera on May 17, 1999. The total integration time is 96 min. Individual pixels (each 0.0455 arcsec wide) are well visible at this large scale. The field of view is about 16 x 16 arcsec 2. North is up and east is left.

These images were taken on May 17, 1999, between 06:50 and 09:50 UT with the VLT Test Camera at the KUEYEN telescope (VLT UT2) at the Paranal Observatory (Chile). The individual images were bias-subtracted, flat-fielded, cleaned of cosmics (dark pixels caused by cosmic rays impacting on the CCD detector) and normalized. The best twelve images were selected, aligned to the same pixel position and coadded. The observing conditions were variable; the seeing was initially about 0.4 arcsec, but deteriorated somewhat during the observations.