Blast from the past
Recently I rediscovered some of those memories in my observing notes and journals. An early morning rendezvous with Jupiter and Saturn, for example, on October 21, 1978, recalls that both planets were well placed in the east an hour or so before sunrise. We were observing with a 6-inch refractor mounted on an old surveyor’s tripod. My drawings show one cloud band of Jupiter as dark and a bit ragged on the upper edge with a hint of a “bulge” on the lower section. The other band was fainter, and we could see little detail on the cloud tops of Jupiter. Europa and Callisto appeared as two starlike objects. Saturn was lower in the sky, but was beautiful as always. The rings were not edge-on, but were partly closed. Unsurprisingly, we couldn’t make out any cloud details with a scope of this size.
The 6-inch refractor we used that morning in 1978 was pretty typical of the kinds of scopes many amateurs used in the 1960s, ’70s, ’80s, and beyond. Browse through the ads of any astronomy magazine of the time, and you will see ads for the Criterion Dynascope RV-6 reflector, Unitron 2.4- and 3-inch reflectors, and the orange squat tube of an 8-inch Celestron telescope.
Resetting the solar system
What we didn’t appreciate fully quite yet, in 1978, was that all of us who were into amateur astronomy were about to have our proverbial socks blown off as Voyager 1 made its close approach to Jupiter in March 1979 and Voyager 2 in July of the same year. The astounding detail of the images returned by these spacecraft forced us to totally rethink not only what we knew about this giant planet, but the solar system as a whole.
In the early years of my planetarium career, I used astronomy books written by Isaac Asimov as an authoritative source for school and public programs. One of those was Jupiter, The Largest Planet. According to Asimov, Jupiter had 13 moons. The Voyagers added three more moons to the realm of Jupiter. Today we count 51 moons with names, and another 18 that orbit anonymously around the giant planet.
Planetary discoveries were happening even before the spacecraft departed. On March 10, 1977, just months before the Voyagers launched, the world learned that Uranus, like Saturn, has a system of rings. MIT astronomer Jim Elliott made the discovery while watching Uranus occult, or pass in front of, a star, to study the planet’s atmosphere and other features. To his surprise, the star faded in and out before it disappeared behind the planet, providing evidence for the rings. Then, in 1979, Voyager 1 revealed that the king of planets, Jupiter, is also surrounded by four thin dust rings.
Flipping through my observing journals, I came across an unusual night several years later, on July 17, 1985. I was observing both Jupiter and Saturn. The Voyager rendezvous with these two gas giants was over, and Voyager 1 was on its way out to the edge of the solar system. That night, I was using a Celestron 8-inch telescope and a range of eyepieces. At about 250x, both planets held up well with clear details. I could see at least five bands on Jupiter and the shadow of the moon Io as it progressed across the disk of Jupiter.
Saturn was gorgeous, as always. My drawing shows the rings almost wide open. I noted one cloud band and the Cassini Division as quite clearly visible. As I watched Saturn drift by in my field of view, I thought of all we had learned about the ringed planet during the past few years. In the C8, I could easily see features that had been observed for the past three centuries. Now we knew that Saturn’s rings were far more complex than what any ground-based telescope could show. In the high-resolution images returned by Voyager 2, astronomers discovered hundreds of thin rings, some only a few feet thick.
Imaging the outer planets
I have always enjoyed drawing what I see in the eyepiece. Many of my contemporaries, however, have produced images of the outer planets using backyard scopes and cameras.
For many years, my go-to book on astrophotography was Outer Space Photography for the Amateur by Henry E. Paul, published in 1960. The book still provides a gold mine of information, covering everything from lenses and telescopes to home observatories and sky conditions. Paul recommends using a standard 6-inch f/8 reflector or a 3-inch f/15 refractor, with a preference for the reflector. Obviously, a telescope needs a motor drive to compensate for Earth’s rotation. But the revolution in CCD imaging and the use of digital cameras has made the techniques described in this book obsolete. Even films recommended by Paul, such as Kodak’s High Contrast Copy Film and Plus-X, have long become extinct.