There is a star chart in Marekai's lair. You can get there through Shay's bedroom.
Could you get Marekai out of the lair and back to his bedroom?
His bedroom can be accessed through the trophy room.
There is a loose panel on the wall. If you fiddle with the wires it will cause an alarm.
Now he is in his bedroom. Quick, grab the star chart!
You have to push the green button to lock the door first. Now, grab the star chart.