Ephemeris is an augmented reality app made for a collaboration between Louis Vuitton Foundation and the DSAA of Jacques Prevert. Visitors are invited to create their own constellation with a simple game of "connect the dots" developed with Unity. Every constellation then appear in a virtual sky in augmented reality, each visitor adds to the sky with his constellation, contributing to a collaborative sky full of stars. Ephemeris are maps of the stars that permitted navigators to find their way in the night. The Louis Vuitton Foundation communicates a lot on its architecture that evokes a vessel. This work was realized in collaboration with Yuan Zhong.