According to Startrek.com, the pronunciation for Galdonterre was "ghel-don-TEER". 
According to the Star Trek: Star Charts (pg. 64), Galdonterre was located in the Galdonterre system, The Galdonterre system was located in or near Klingon space, in the Beta Quadrant. This was a single star system. Primary of this system was a Class K star with a magnitude of +7, which was 1/10 as bright as Sol.