The AXAF Deep Field

This image displays a 0.5° x 0.5° sky area in the direction of the so-called AXAF Deep Field in which few bright objects are seen. This photo results from the combination of 28 individual WFI exposures behind a B(lue) optical filter with a total exposure time of 7 hours. About 100,000 galaxies are visible in the original image that encompasses approx. 8000 x 8000 pixels (1 pixel = 0.24 arcsec). The light trail of an artificial satellite crosses the field. The High-Res version included here has been compressed by a factor of four in order to facilitate transport over the Web. North is up and East is left.

Twenty-eight exposures with a total integration time of 7 hours have been co-added. After each single exposure, the telescope was offset by a small angle in order to cover also the gaps between the eight CCD's in the mosaic and to enable removal of minor cosmetical blemishes of the detectors. Since the CCD mosaic of the WFI comprises 67 million pixels, a total of 1,900 million data points was thus used to construct this image. The related image processing, using the EIS WFI data reduction pipeline, recently developed at ESO, kept a powerful workstation fully busy for about 8 hours.