JoinScope on the Skies: Tracking planets around the Sun
In earlier columns, the celestial coordinate system of hour circles of right ascension and degrees of declination was introduced along with the use of an equatorial star chart (see SFA Star Charts in Resources). This system shows the planets’ motion relative to the ecliptic, the apparent path the Sun follows during the year. An alternate system, using heliocentric longitude, places the viewer in an above-the-solar-system viewpoint, tracking the planets in their near-circular orbits around the Sun.