Complex sentence: For longitude, the zero point is the Prime Meridian on the geographic equator; for right ascension, the zero point is known as the first point of Aries, which is the place in the sky where the Sun crosses the celestial equator at the March equinox.
Split into simpler sentences: For longitude, the zero point is the Prime Meridian on the geographic equator. For right ascension, the zero point is known as the first point of Aries, which is the place in the sky where the Sun crosses the celestial equator at the March equinox.