What are the special MORE and PREVIEW catalog columns?
There are two special (optional) catalog column names: MORE and PREVIEW. They are expected to contain a URL in the format M=http://… for MORE and P=http://… for PREVIEW. The MORE URL should point to an HTML page with more information on the object. skycat passes the URL to netscape for display. The PREVIEW URL should point to either a FITS image (possibly compressed) of the selected object or a tab table with data to plot as an X,Y graph. The Content-type of the HTTP result is used to determine whether the data is a FITS image or a tab table and whether or not it is compressed. The Astronomical Server URL document mentioned above describes the allowed Mime-type/Content-type values. These have been implemented in skycat. If the Content-type of the PREVIEW data returned from an HTTP server is recognized as a tab table (text/x-starbase, etc., or even text/plain), it it should be an ASCII tab table with 2 columns. The first column is plotted as X and the second as Y and the column head
