Astrobrowse Home page Users can select pre-defined sets of resources. Currently only one such pre-defined set is available. This queries about 20 distinct resources in many wavelength bands. The user can then go to the next step of specifying the region of interest. The second mechanism for selecting resources is for users to explicitly choose the resources of interest.
Some resources are recursive.
Rather than pointing to external resources they point to lower level Astrobrowse pages. E.g., the Vizier service at the CDS has about 700 catalogs available through Astrobrowse. It would be infeasible to have a form listing all of these. Instead the main form has an entry for each of a number of categories of these catalogs. When a user chooses one of these he or she can later choose any catalog from within this category.