Once you are attuned you will be able to discover NEW Constellations. Simply by looting Constellation Paper you get from chests you can discover seven new Constellations. Unlike the basic Constellations, you will not be able to bind yourself to these, but you can bind Crystals to these. When looking in the Tome you will notice that these seven new Constellations are a different colour to the other ones.
Unlike the previous Constellations, when you are trying to attune a Crystal to these new Constellations you will notice that it might take a few days for the Altar to activate. This is normal.