Hi, Comet and asteroid are not "catalog". The Astrob or MPCORB files do not contain directly the required position but elements to compute the position at a given date. You cannot use Catgen with them.
With V3 go to Setup / Solar system / Asteroid (Comet) to download the elements directly from the program. You can select which file to download from Setup / Internet / Orbital elements. Beware the full asteroid file is big and take time to download and process. Also have a look at the documentation http://www.ap-i.net/skychart/en/documentation and specifically http://www.ap-i.net/skychart/en/documentation/quick_start_solar_system Patrick
