... Known as an equinox, this astronomical event marks the first day of spring in the northern hemisphere and autumn in the south. ... Equinox means equal night. Saturn: Moons in Transit . ... Martian Moon Deimos from MRO . ... Deimos is one of the smallest known moons in the Solar System measuring only about 15 kilometers across. ... Hickson Compact Group 90 . ... The catch is, this lunar X is only apparent during a four hour period just before the Moon's first quarter phase. First page ] Prev. ...