C2A is able to download some catalogues directly from the Internet. At this time, only the USNO-B1.0 catalogue can be accessed in this way. You access this dialogue box by using the Remote Catalogues... command in the File menu. To get information on one of the components of this dialogue box, left-click on it in the image below:
Note that for the USNO-B1.0 catalogue, the field specified must not be more than 4°.