y use faint galaxies to define the reference frame, and in  addition to measuring paral ax, the precise measurement of this quantity was the major goal of the  Hipparcos satel ite.
In 1996, Eckart and Genzel used speckle interferometry to measure this quantity and found that its  distribution is centered on the purported position of Sagitarius A-star. Measuring this quantity for water masers associated with galactic centers makes it possible to directly determine the distance to the galaxy.  Surveys for measuring this quantity typical y use faint galaxies to define the reference frame, and in  addition to measuring paral ax, the precise measurement of this quantity was the major goal of the  Hipparcos satel ite. Typical y measured in arcseconds per year, for 10 points, identify this astrometric  quantity which measures the change of position of an object on the celestial sphere, factoring out  change-of-coordinates phenomena such as precession.
In 1996, Eckart and Genzel used speckle interferometry to measure this quantity and found that its  distribution is centered on the purported position of Sagitarius A-star.
proper motion