We may distinguish several facets to the task of retrieving information on a given astronomical object. To find out what has been published on that object, a good start is made by consulting the various object databases (Section 4.1) and looking at the bibliographical references returned by them. Some basic data on the object will also be offered, but to retrieve further published measurements a detailed search in appropriate catalogue collections will be necessary (Section 4.2). Eventually one may be interested in retrieving and working with raw or reduced data on that object such as spectra, images, time series, etc., which may only be found in archives of ground- or space-based observatories (Section 4.3).
Only objects outside the solar system will be discussed in this section. Good sites for information on solar system objects are NASA's ``Planetary Data System'' (PDS) at JPL ([Planetary and Space Science (1996)]; pds.jpl.nasa.gov and ssd.jpl.nasa.gov), the ``Lunar and Planetary Institute'' (LPI; cass.jsc.nasa.gov/lpi.html), the ``Solar Physics'' and ``Planetary Sciences'' links at the NSSDC (nssdc.gsfc.nasa.gov/solar and .../planetary), and the ``Minor Planet Center'' (cfa-www.harvard.edu/cfa/ps/mpc.html). The ``Students for the Exploration and Development of Space'' homepage also offers useful links on solar system information (seds.lpl.arizona.edu).