Idini Star Cluster
The Idini Star Cluster was a stellar cluster which a starship would transit through when traveling from Persephone V to Mordan IV. This cluster was located somewhere in the Alpha or Beta Quadrant.
In 2364, the USS Enterprise-D passed through the Idini Star Cluster on its way to Mordan IV. Admiral Mark Jameson piloted the ship through, since he was familiar with the cluster. (TNG: "Too Short A Season")
This stellar cluster was only mentioned in dialogue.