[f. ASTRO- + Gr. -μετρία measurement.] The measurement of the apparent relative magnitude of the stars.
1847. Sir J. Herschel, Astron. Obs., 1834–8, iii. 304, Chapter title, Of astrometry, or the numerical expression of the apparent magnitudes of the stars.
1867–77. Chambers, Astron., 913.
