BLINK MICROSCOPE, an auxiliary astronomical instru ment. Two photographic plates of the same star-field taken at different epochs are placed in the machine and viewed one with one eye and the other with the other eye, and adjusted as in a stereoscope so that a single visual impression is given. An arrange ment is provided by which the plates are alternately in rapid succession hidden from sight. Attention is at once called to any star image which has changed in the interval between the two epochs by the corresponding flicker. In this way variable stars and stars with large proper motion are detected.
Proper motions can also be detected without the flicker arrange ment, since the displacement of the star-image gives a stereo scopic effect, the star appearing to stand out in relief in front of or behind the plane of the other stars. When used in this manner the instrument is called a stereocomparator.