ephemerist

plural ephemerists

1. One who collects or studies ephemera.

   The true ephemerist is as committed to the smallest neglected fragment as to the spectacular 'collector's piece'.

   1988, Maurice Rickards, Collecting printed ephemera, page 30

2. One who studies the daily motions and positions of the planets.

   the night immediately before he was discoursing of, and lighting the art of those foolish Astrologers, and Genethliacall Ephemerists

   1640, I. H. [i.e., James Howell], ΔΕΝΔΡΟΛΟΓΊΑ [DENDROLOGIA]. Dodona’s Grove, or, The Vocall Forrest, London: […] T[homas] B[adger] for H. Mosley [i.e., Humphrey Moseley] […], →OCLC

3. One who keeps an ephemeris; a diarist.