Equuleus, ( Latin: “Little Horse”) constellation in the northern sky at about 21 hours right ascension and 10° north in declination. Its brightest star is Kitalpha (from the Arabic for “part of a horse”), with a magnitude of 3.9. Ptolemy referred to this constellation as the head and neck of a horse, but, unlike most other northern sky constellations, it was never identified with any story from Greek mythology.