Get outside about and hour or so after sunset and be treated to the Saturn and Jupiter show! Later in the evening is even better as Saturn is prominent in the south/southwest and Jupiter climbs in the southeast.
Saturn was at opposition on August 14th and Jupiter is heading for a September 26th opposition, making them bright and fully lit for our viewing pleasure.
What is opposition? Think Full Moon. Every month, when the Moon is full, it’s at opposition. It’s in the opposite side of our sky as the Sun. The Sun is setting in the west while the Moon rises in the east. That’s opposition. All the planets outside Earth’s orbit (Mars, Jupiter, Saturn, Jupiter, Uranus, and Neptune) get to be in opposition. The inner planets Mercury and Venus don’t get to opposition; hence, they are never fully illuminated as seen from Earth. The best illumination they get from our perspective is during their greatest elongation (their largest angle away from the Sun).
Saturn rises first, just after sunset, and is about 30 degrees high in the south by 10 pm. Jupiter rises about an hour later and is visible in the southeastern sky about an hour after sunset.
If you can magnify Saturn by 50x, you will be able to easily see the Cassini Division – a clear area between the A ring (outermost) and B ring. You will also be able to see Saturn’s creamy yellowish color and maybe Titan, Saturn’s largest satellite.
Bumping the magnification up to 200-250x really brings out the Cassini Division and you might be able to glimpse the Encke Gap, a very thin clearing near the outer edge of the A ring. With careful inspection, the C ring, aka Crepe ring, inside the B ring might be seen. It looks like a faint shadow or darkening of Saturn inside the B ring.
With larger aperture (8” or greater) and higher magnification (>200x), phenomena such as Saturn’s southern hemispheric blue hue might be seen.
The B ring sometimes exhibits a phenomenon called spokes, radial darkening that looks like spokes, thought to be caused by electrically charged dust particles. The particles appear to be affected by Saturn’s magnetic field, appearing, dissipating and reappearing. They are expected to be visible this September when Saturn is at opposition. Don’t get too excited, you will need a larger scope (10” or greater) and high magnification (around 800-1200x) to get a look at the spokes. Stephen James O’Meara observed them with Harvard’s 9” refractor in 1976, but he is known as a superb observer.
Saturn’s subtle cloud belts and zones are a challenge but can be visualized. Saturn has spots too, and they are very subtle, except for the Great White Spot. Thought to be caused by huge storms below, the Great White Spot is a frozen water cloud and tends to smear with Saturn’s strong winds. We might get lucky and see a Great White Spot this September.
Happy hunting, we’ll look at Jupiter next week.