For unknown reasons the GAIAStars2.skydat file has been created on two locations on my hard disk by SkySafari 6 Pro : in the Library / Application Support folder of the system and in my own Library / Application Support folder.
I would not mind if these files had not a size of 1.65 GB !!!!
These files are linked to the database extensions of SkySafari but there is probably one too much.