The Nine Planets

A One Night Solar System Marathon

Observing at Henry Coe SP, 1996 Oct 14

Planning for this weekend's (1996 Oct 14) observing session, I noticed that it would be possible, if the weather cooperated, to see all nine of the planets in our solar system in a single evening, an irresistable possibility to me as the author of The Nine Planets. The weather did not cooperate on Saturday but as Sunday evening approached with the cloudless deep blue skies I was on my way with high hopes to one of my observing spots, Henry Coe State Park, just south of San Jose, CA.

The evening started well with a beautiful thin crescent Moon only 36 hours old. I was afraid I would miss it so I stopped half way up the hill just at sunset and searched with my binoculars using my laptop computer as a guide. After some searching I found it, the youngest Moon I have yet seen. By the time I got to the observing site about 10 minutes later, it was totally obvious to the naked eye. Sometimes you don't need all the fancy technology :-)

On this occasion, it was possible not only to see all nine planets but also to observe them "in order". So Pluto was first and, of course, by far the hardest. (Yes, I know that Neptune is slightly farther from the Sun right now, but Pluto was pretty near the western horizon so it had to be first.) After quickly aligning my trusty 12" Meade LX200, I punched up Pluto on the keypad to see if I could match the star field to a printed chart I had printed showing Pluto's position for that day. As usual, I forgot to print the chart with left/right reversed so mental gymnastics were required. Nevertheless it was immediately obvious that the LX200 had hit the right field and that Pluto was not be be seen. But at this point the sky was not quite dark so a bit patience was called for. And by 8pm it was rewarded! With averted vision (and firm knowledge of the right position) Pluto came into view about 20% of the time. Not very interesting visually :-) but with Pluto in the bag, rest of my marathon was all downhill.

After a few key presses and loud gear whining later, Neptune's tiny deep blue disk appeared in my eyepiece. My computer told me where to look for Triton but no luck this time.

On to Uranus, a featureless pale blue dot. But there are 4 moons to try for. With foreknowledge of their positions and averted vision I was able to see Titania and Oberon; Ariel and Umbriel were visible only with averted imagination (a powerful but suspect technique!).

When it is well placed, Saturn always steals the show. And justifiably so! Lots of moons, features on the disk, and the fabulous rings; what more can you ask for? This was not a good evening for Saturnian moons, though, I was able to see "only" 5: Titan, Rhea, Dione, Tethys and Hyperion.

Jupiter and the four Galilean moons were easy, of course. Observers farther west got to see an Io shadow and transit, but I was content in the knowledge that I had now observed 99.9% of the mass of the solar system (aside from the Sun, of course).

After a quick peek at Comet Hale-Bopp it was time for the long wait until dawn and the inner planets. Fortunately, there were a couple of astrophotographers nearby who had a lot of time to chat during exposures.

A couple of nasty bands of clouds tested our faith at this point for a couple of hours. Two of the photographers gave up and went home muttering about having to work or some such mundane irrelevancies. Those of us with less sense and more dedication were rewarded with perfectly clear skies until dawn.

Mars was up by 3am. But even later when it was high enough to be seen clearly, no detail was visible. Mars' time will come in the spring.

The third planet from the Sun is pretty obvious, even at night :-)

Comet Tabur was well up by this time, too. Its almost featureless with no nuclear condensation apparent; it looks like a giant elliptical galaxy. At least one degree of tail was visible, too.

Blindingly bright Venus rose about 4am and was visible until well after sunrise. Nothing much to see except the gibbous phase.

By 6am with most of the stars lost in the dawn light, Mercury. The silly software in the LX200 usually won't slew to Mercury saying that it is "too close to the Sun" even though the Sun is well below the horizon. But no matter, it will slew manually. I actually caught a glimpse of Mercury through the trees on the horizon and was able to watch it rise. It put on an interesting show, actually. The refraction of the Earth's atmosphere broke Mercury's image into a constantly shifting and shimmering blob of bright color. The image was often spread out into a line up to ten times longer than it was wide with all the colors of the rainbow from deep red to dark purple clearly visible. Not very interesting astronomically but very pretty.

And last, but definitely not least, the Sun. All in all, I saw 9 planets, 12 moons, two comets and the Sun: 24 solar system objects (plus a few meteors) in one night.

Bill Arnett; last updated: 1996 Nov 16