Click on its name to go to the home page of any of these satellite observatories.
Hubble Space Telescope (HST) -- Compton Gamma-Ray Observatory (CGRO) -- Chandra X-Ray Observatory (neč AXAF) -- Space Infrared Telescope Facility (SIRTF)
Cosmic Background Explorer (COBE) -- Far-Ultraviolet Spectroscopic Explorer (FUSE) -- Hipparcos -- Infrared Space Observatory (ISO) --Roentgen (X-ray) Satellite (ROSAT) -- Solar and Heliospheric Observatory (SOHO)
Anglo-Australian Observatory (AAO) -- European Southern Observatory (ESO) -- Gemini -- Hobby-Eberly Telescope (HET) -- W.M. Keck Observatory -- National Optical Astronomy Observatory (NOAO) -- Palomar Observatory -- Stratospheric Observatory for Infrared Astronomy (SOFIA)
Arecibo Observatory -- Australia Telescope (ATNF) -- Caltech Submillimeter Observatory (CSO) -- National Radio Astronomy Observatory (NRAO) -- Nobeyama Radio Observatory (NRO) -- Owens Valley Radio Observatory (OVRO) -- Very Long Baseline Array (VLBA)
The comprehensive index to on-line astronomical pictures and simulations is the NRAO Pretty Pictures page. Some of my favorites among the sites listed there are the following.
1. Nice radio images of quasars and other active galaxies, mostly made with the Very Large Array (VLA), abound on the staff Web pages at the National Radio Astronomy Observatory (NRAO). I particularly like those in Dr. Alan Bridle's gallery.
2. A good place to find the best Hubble Space Telescope (HST) images is the SEDS Best of HST site.
3. The Anglo-Australian Observatory (AAO) is home to the all-time greatest astronomical photographer, David Malin. To gain a proper appreciation for Malin's work one must really see large-format high-quality prints of them (preferably made by Malin himself), but one can get started on the low-resolution copies of some of his best pictures at the AAO Web site.
4. One often wants to see pictures of objects for which one knows a Messier (M) or New General Catalogue (NGC) number. These can be found in a variety of spots, like the Astronomical Society of the Pacific, the University of Nice, the University of Oregon, and the ubiquitous SEDS .
Much more extensive on-line astronomy resources are available from the Space Telescope Science Institute's (STScI) Astro Web and from pages linked to the American Astronomical Society (AAS) Home Page .
Astronomical data and journal papers
Check out the NASA Astronomical Data Center (ADC) for a large, downloadable collection of images, catalogues of objects, and tabular data from published articles.
In the same vein, the National Space Science Data Center (NSSDC) has a separate space-astrophysics section amidst the definitive collection of images and data on space-flight missions and space and planetary science.
The Base des Ames (BDA), a comprehensive collection of data on stars in open clusters, is extremely well-designed, useful, and up to date.
The NASA Astrophysics Data System (ADS) includes a searchable collection of all the major astrophysics journals, in most cases going back to the first volume, from which articles can be downloaded or printed in a variety of manners. I recycled my entire Astrophysical Journal collection a while back, and this is why.