Astrometry is the science dealing with the positions and motions of celestial objects. Astrometry is essential in modern astrophotography where capture software like N.I.N.A, Ekos, APT or others, plate solve the images in order to obtain an astrometric solution, meaning they will precisely know the position of the frame with regards to the sky. Astrometry can also be used at processing stage, like in photometric color calibration tool for example.