Update >> comet elements the log file is in here: C:\Users\ yourusername \AppData\Local\skychart\database right now it is using from van buitenen 's database http://astro.vanbuitenen.nl/cometelements?format=mpc&mag=obs the update may take some minutes, just be patient For kstars in linux, it seems the auto update is not working (NASA JPL link down?) comets.dat is located in /usr/share/kstars I copied the file from van buitenen website you have to be root to replace it ( eg in terminal)