OpenSkyQuery allows sophisticated queries of astronomical catalogs in a uniform way, as well as cross-matching published catalogs. The driver is a general and powerful query language. A personal catalog of objects can be imported and cross-matched with published catalogs.

To illustrate Open Sky Query, we use the following sample question:

What are the Near Infrared colors of bright quasars discovered using blue excess selection criteria?

Through the NVO registry, a number of quasar surveys with accessible catalogs can be identified. We select, for example, to use the 2DF Quasar Redshift survey (2QZ) as our source of confirmed UV excess selected quasars. A file containing simple text, or VOTable information (RA, Dec, etc.) for many objects can be uploaded to Open Sky Query, via the Import page, for comparison with an all sky infrared survey like 2MASS.