Caption: Saturn as seen from the perspective of Earth over the time period 1996--2000. Time increases going from lower left to upper right.

Features:

1. The water ice fragments (ranging in size from ∼ 1 cm to ∼ 10 m: see Wikipedia: Rings of Saturn: Physical characteristics) that make up Saturn's rings orbit in the plane of Saturn's equator. Saturn's equator and the coplanar Saturn's rings have a tilt of 26.73° to relative to the Saturn's orbital plane which inclined relative to the ecliptic plane by only 2.485°.

2. The Saturnian equator and Saturn's rings and their perpendicular the Saturnian rotational axis probably have an axial precession (relative to the observable universe). However, it is probably much slower than the Earth's axial precession since Saturn has much more angular momentum than the Earth, and so its orientation (relative to the observable universe) has much stronger resistance to gravitational perturbations. So axial precession of Saturn is very unnoticeable and is NOT what we see in the image.

3. As viewed from the Solar System barycenter (which is approximately the center of the Sun), Saturn's rings will be seen edge-on twice per Saturnian year (29.4571 Jyr) at the Saturnian equinoxes when Saturnian rotational axis is perpendicular to the barycenter-Saturn line. Recall the Julian year = 365.25 days exactly by definition.

4. Since the Earth is always about 1 AU from the Solar System barycenter and the Saturnian mean orbital radius = 9.5826 AU, the Earth's perspective is approximately that of the Solar System barycenter, and so we see Saturn's rings edge-on once or three times in a edge-on-viewing period of about a year that happens twice every Saturnian year (29.4571 Jyr) on average at about the Saturnian equinoxes (see Wikipedia: Rings of Saturn: Saturn's axial inclination). Because of the Saturnian orbital eccentricity = 0.0565 = 5.65 % (and other orbital features), the periods between Saturnian equinoxes are NOT equal: they are about 13.7 years and 15.7 years: these periods, of course, add up the Saturnian year (29.4571 Jyr). So the edge-on-viewing periods are NOT equally spaced in time: they are 13.7 years apart and then 15.7 years apart and then ... and so on.

   An edge-on-viewing period (with 3 edge-on views) occurred 1995--1996 (see Wikipedia: Rings of Saturn: Saturn's axial inclination). The lower left view of Saturn in the image probably shows Saturn shortly after the last edge-on view in 1996.

5. Because Saturn's rings are very flat---ranging from ∼ 10 m to ∼ 1 km thick (see Wikipedia: Rings of Saturn: Physical characteristics)---the Saturn's rings practically vanish at an edge-on view.

6. Saturn's rings are most full at about the two Saturnian solstices which happen twice a Saturnian year (29.4571 Jyr) at about midpoint times between the Saturnian equinoxes.

7. For a bit of astronomy history, Galileo (1564--1642) was the first to observe Saturn's rings with his Galilean telescope in 1610, but he could NOT determine what they were---planets? appendages?---he described them sometimes as "ears". When Saturn's rings vanished in an edge-on view in 1612, Galileo commented "Has Saturn swallowed his children?" referring to the myth of the Greek god Cronus (who was syncretized to the Roman god Saturn) swollowing his children---they got out later on. For reference, see Wikipedia: Rings of Saturn: Galileo's work; Wikipedia: Galileo: Saturn and Neptune. Christiaan Huygens (1629--1695) in 1655 was the first to propse that Saturn had a planetary ring and viewing the planetary ring nearly edge-on caused the periodic disappearance of the planetary ring (see Wikipedia: Christiaan Huygens: Saturn's rings and Titan; Wikipedia: Rings of Saturn: Ring theory, observations and exploration).