March Madness, Astro-Style

Saturday evening, March 17th-18th, I made the trek with fellow South Bay Astronomical Society (SBAS) members to our observing site near Red Rock Canyon State Park for a night of dark-sky observing. As the "new moon" weekend in March, this would be the best time to attempt a Messier Marathon - an annual adventure in which astronomers attempt to view all 110 Messier objects in a single night. Having completed a marathon in 2004, I was more interested in another event which, coincidentally, was anticipated that same evening - an occultation of Pluto.

An occultation is an astronomical event in which two bodies line up so that from one's position on Earth, one appears to "cover up" (or occult) the other. In this case, distant Pluto was predicted to pass in front of a still-further-distant star. Such an event is interesting to astronomers, because careful observation during the occultation can tell us a lot about either body, or both. It's known that Pluto has an extremely tenuous atmosphere. Observations of how the light from the distant star is diminished when Pluto passes in front of it can yield important information about the nature of that atmosphere.

This particular occultation was much anticipated, because calculations of its path predicted it to be visible across much of the SouthWestern US where many professional and amateur astronomers would have an excellent view in the pre-dawn hours. The amateur community had been asked to participate in this rare event by collecting CCD video sequences and submitting them to the professional community for analysis. However, both Pluto and the occulted star are very faint objects - difficult to see even under very dark skies using large amateur telescopes. Hence, the dimming of the star would likely not be visible to the naked eye. A sensitive CCD camera would be required to really measure the event. However, I took it as a challenge to at least find Pluto at the appointed time.

Since the occultation was to occur in the early morning, I had the entire evening for other pursuits. I arrived at our familiar site just after sunset and had just a little time to unpack and setup before complete darkness fell. A half-dozen other members were already in place and ready for a night of observing. Several were "marathoning", others planned to concentrate on CCD imaging. This would be my first attempt to power my laptop from the car battery, using a small DC/AC inverter. I had mixed results, as the inverter worked, then seemed to quit inexplicably, only to work again later in the evening. Further fiddling is required.

Venus commanded the western sky through twilight. In the scope, it was a tiny gibbous, still quite distant - having only recently emerged from behind the Sun in its race to catch Earth on its faster, "inside" orbit. Magnificent Orion stood in the southwest and when the last light of day left the sky, the awesome vault of the winter Milky Way stood high overhead, spanning the sky from horizon to horizon. The first full-dark view of the night sky at a dark location never fails to inspire awe. In fact, I'm surprised and delighted by the effect it has on me, each and every time. It is a faithful reminder of the cosmic grandeur around us - and of how much of that grandeur is out of reach in our brightly-lit cities!

The desert wind had eased a bit, but did not die completely, gusting occasionally during the night, reminding us to secure loose papers in our work areas. A bit annoying, but I've weathered far worse windy evenings at this location! To start the evening, I concentrated on the available winter constellations - Orion, Canus Major, Canus Minor, Gemini, Cancer, Auriga and others - using Sue French's excellent Celestial Sampler as my guide to explore a host of lesser-known deep-sky objects and interesting stars. A compilation of her many articles in Sky & Telescope magazine, this book is an excellent season-by-season guide. If you have worked over the Messier catalog and are ready for other delights, check out this book.

By 11pm, I'd logged several dozen new objects and was ready to catch a couple of hours sleep before rising again to pursue Pluto. So, I set my wrist alarm and crawled into the back of my Explorer. The alarm sounded too quickly at 3am! I was pleasantly surprised to discover the night hadn't gotten too cold and quickly set up my task of finding Pluto. At 14th magnitude, it proved to be just at the edge of visibility in my 11" Celestron. In fact, my initial identification was incorrect. But with the help of a compadre and his excellent star maps, we managed to correct identify it - at least we're fairly confident we did! Through the process, I learned to appreciate how important a sensitive CCD imager would be to measure any sort of occulting effect!

The air was dry and reasonably warm, and in the early morning sky the familiar summer constellations - Scorpius, Sagittarius, Ophiuchus, Hercules and others - had risen to viewable height. I was compelled to explore the morning sky in the remaining hours before twilight. Jupiter beckoned brightly between Scorpius and Sagittarius and the summer Milky Way reminded me of the pleasures of dark summer skies in the months ahead.

When finally the eastern horizon lightened and the last of the stars winked out in the spreading dawn, I crawled back into my sleeping bag for a final hour of sleep before packing up and heading home. Once again, a fine night of viewing!