about my cover page picture :

The picture above was taken from STSCI press release STScI-2000-07, dating January 24, 2000, with further information and more images from Andy Fruchter's webpage at STSCI. It shows the planetary nebula NGC2392, also known as the "Eskimo Nebula", observed with HST after Space Shuttle servicing mission STS-103 on January 10 - 13, 2000. The picture shows a combined image from four drizzled narrow band filter exposures, taken with the Wide Field and Planetary Camera 2 (WFPC2). The following filters were used: F469N (HeII), F502N ([O III]), F656N (H alpha), and F658N ([N II]). The total exposure times for these filters were 1400, 400, 400, and 1400sec, respectively.

This beautiful picture shows a remarkable wealth of detail, which, for obvious reasons, cannot be obtained from the ground. For comparison, the following frames show narrow band pictures in H alpha, which were obtained as part of my thesis project using the Wendelstein Observatory 80cm Telescope with MONICA. The first frame is the fully reduced, but else unprocessed CCD image which was obtained under 1.5arcsec seeing. Frames no.2 through 4 show this image after deconvolution using the Richardson-Lucy algorithm at different contrast levels. Your browser should open a new window to display these frames and allow you to blink between the different versions. Evidently, the processed ground-based image is revealing most of the prominent features of the HST image. However, the presence of several artefacts demonstrates also that  the method has its limitations.

  Andy Fruchter's drizzled HST image
  deconvolved MONICA image, medium contrast
  deconvolved MONICA image, low contrast
  deconvolved MONICA image, high contrast
unprocessed MONICA image