The Star Chart artifact can be found in Executioner's Watch, in the north-eastern part of Sea of Núrnen.
Mysterious star chart Bone, Late Second Age
Carved from the bone from an unknown animal of immense size, this map of the heavens was no doubt used by a Lore Master of some skill. Only a few select individuals would have been able to use this chart to track the course of the stars in the skies, using complex and, possibly, arcane computations to predict the future.
"…By that time we'd grown used to seeing them, but the shorter one had grown cold, distant. He could read the leaves, the lines in a man's hand, the bumps on his head. He could see, you know? And I guess it got to him. The knowing.
They'd go off together, and you could tell when they met up with the Orcs. The sky would darken and there'd be hail, or rain, or winds that shook the trees. And then, sure enough, everything would clear. They never spoke about any of that, although we'd always want to know. ""Best not,"" they'd say.
The two left without saying a word. Only it was funny, like, because the shorter fellow left behind all his maps and the odd little board he used to see into the future. Traveling light, maybe, or maybe… I don't know, maybe he thought he'd have no more use for it."