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An Eclipse, a Near-Graze, and a Comet

Fiona Hobson


As the Full Moon rose on May 4, I had much to look forward to: a Total Lunar Eclipse, a graze or near-graze of the Moon by the double star Alpha Librae, as well as a good look at comet NEAT once the bright moonlight was extinguished.

Right on time, the Moon touched the edge of the Earth's umbral shadow at 20:48. Alpha Librae was dimly visible nearby, more than the Moon's diameter away. My telescope revealed it as a widely-separated double star, with the dimmer component closest to the Moon. With the naked eye only the brighter one (Alpha-2) was visible in the dazzling moonlight.

I watched as the earth's shadow rapidly gobbled up the Moon's craters. First Plato, then Archimedes, then Copernicus vanished into the darkness. By 21:30 the Moon was more than half darkened, and the Alpha Librae pair was much closer, now about half the Moon's diameter away. The sky was darker, and the Milky Way was beginning to appear.

The last sliver of sunshine disappeared from the Moon at 21:52. The Moon became a deep pinkish-brown. The night was wonderfully dark. Alpha Librae, now looking much brighter, was a quarter of the Moon's diameter away, so I still had time to swing the telescope round for a quick look at comet NEAT C/2001 Q4.



(above) Mauritz Geyser captured the eclipsed Moon and Zubenelgenubi at about 20:30 UT using a 8-inch f/5 telescope with a Minolta X-300 camera and Fuji Sensia 400 slide film. (below) A 21-minute sequence showing the Moon moving past Zubenelgenubi, as seen from Pretoria. More images are available at



The comet was next to the hindleg of Canis Major. In the darkness of the total eclipse it was faintly visible to the naked eye. In mid-April when I had first started watching it, the comet had not been visible to the naked eye at all, and recently the bright Moon had drowned it out. Now I was glad to see that it had brightened a little. The telescope showed a distinct bright nucleus, surrounded by a large diffuse coma. The coma was slightly elongated in one direction, and extended faintly for some distance, but it didn't look at all like the classic comet tail that people see in pictures and that makes them think that a comet streaks across the sky like a meteor. This comet seemed to be just lazily drifting there, surrounded by its large cloud of softly floating mist. Neat.

By the time I turned back to look at the Moon, the double star was almost right underneath it. To the naked eye it was the most stunning sight: a large pink globe hanging there with a bright star twinkling beneath it, almost touching it. My husband, returning from a late and distant farmers' meeting, told me how he kept stopping the bakkie to get out and look at the Moon, so arresting was the sight.


(above) Dany Duprez imaged the Moon/star occultation from Cape Town.

Our farm is at 32°53.6S, 24°21.8E, almost on the "graze-track" for Alpha-2 Librae. I wasn't sure whether I would see the star actually graze the Moon, or whether it would just pass close by. As the time approached I kept my eyes glued to the telescope so as not to miss anything. At 22:35 Alpha-1 and Alpha-2 were each just beneath the Moon, sliding past it. By 22:40 Alpha-2 was almost touching the huge curved edge, but by 22:45 the star was beginning to draw away again.

No graze or occultation for me, no blinking out of the star as it passed behind the mountains of the Moon. Just a near-graze. But what a sight it was. To see such a bright star so close to the totally eclipsed Moon was quite beautiful. It looked even lovelier at about 23:10 when a sliver of brightness had already returned to the top edge of the Moon and the double star was still close by.

They say it'll happen again in 2050. Worth waiting for....




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