Yup. That appears to be beyond the max drawing distance for STC objects.
You seem to be doing better than I am. The maximum distance that I can persuade the Windows version of Celestia v1.6.1 (downloaded from SourceForge) to draw stars is between 10.22 and 10.23 M LY, maybe within about 100 LY of the latter..
A workaround might be to use DSC objects instead: a Nebula with a Mesh that looks like a star, for example. Unfortunately, orbits, planets, and similar objects won't work with them.
DSC GlobularClusters aren't drawn correctly that far away, either.