In the Gaean Reach Gazetteer there area a few stars and planets listed as being part of the Rigel Concourse which don't orbit Rigel and aren't part of Jack Vance's list of 26 planets. Aloysius which actually orbits Vega is the first. The star Pi Cassiopeia is listed as part of the Concourse as well. Vega is listed as one of the stars which make up the Rigel Concourse which must be incorrect,. Also the planet Quinine which is part of the Concourse and does orbit Rigel is listed as orbiting Alphard the Lonely which is no where near Rigel.. I have tracked down the Pi Cassiopeia and so on to an error in translation!. In a rather complicated sentence with a lot of semi-colons in 'Star King' (p40 of the Coronet edition) Jack Vance refers to planets and their stars as follows:
Alphanor: Rigel Concourse
Cuthbert, Boniface and Aloysius: Vega
Noval: no star listed
Copus and Orpo: Pi Cassiopeia
Quantique: no star listed.
As the sentence starts with the Concourse is may have been thought that all the following were planets of the Concourse rather than separate entries in a list.