Astronomy

Moon over Antares

Posted 2007 May 06 @ 10:21 - filed under Astronomy news.
Updated 2007 May 14

As the Moon orbits the Earth, it's path across our night sky repeats itself, but in a very complicated way. It so happens that the Moon is currently going through a sequence of occultations of Antares (I wrote more about this in the ASSA's Sky Guide).

One such occultation took place on Friday, May 04. Seen from Southern Africa, the Moon was below the horizon at the start of the occultation, but soon after the pair rose, the Moon moved away, uncovering the Scorpion's alpha-star.

Carol Botha of Cape Town, and Gustav and myself, attempted to photograph the pair. We knew it would be a challenge: the Moon and star are very different in brightness so the correct exposure would be tricky. Even worse, at the time of reappearance, Antares would be only some 2° above the horizon.

The lovely Cape fold-mountains around Stellenbosch don't give the flattest of horizons, so we drove to the head of the Franschoek valley, near Simondium, and found a good spot. Equipment set up along a farm road gave the Friday-night revellers pause for thought, no doubt.

We waited patiently, scanning the horizon through the valley's mist for the signs of the rising Moon. And then it burst into view, a bright light growing over the distant mountains: Moonrise.

moonrise

(19:21, f/3.5, ISO 80, 15 sec, lens at 6mm (36mm in 35mm-format equivalent))

Not long afterwards, Gustav confirmed he could see Antares appearing just above the Moon; I zoomed in with the digicam and there it was. The seeing was horrible because of the ridiculous altitude, but Antares was unmistakeable.

moon antares

(left: ISO 200, f/3.5, 1/60sec, 12x opt.zoom + 4x digi.zoom = 1730mm; right: ISO 200, f/4.0, 1/125sec, 60mm)

At the same time, over in Cape Town, Carol was also photographing the reappearance. "The soonest I could get it was at 19:27," she writes. "I drove to the nearest hill, but the Moon only came up at 19:25." Her photo below nicely captures Antares while preserving detail on the Moon's surface, despite the terrible light poillution from the Tygervalley shopping centre.

moon antares

(Canon EOS 400D, ISO 800, f/5.6, 1/50th. © Carol Botha)

Near the northern end of the country, from Louis Trichardt, Kos Coronaios of the Soutpansberg Astronomy Club used a Meade 10-inch and a Canon EOS 30D to capture the scene. Antares was just 5° above the horizon at 19:18 when Kos took the image below.

moon antares

A few minutes later, he got this next image, a close-up showing the sharply-defined Mare Crisium directly below Antares and bisected by the terminator, while to the right the terminator crosses the larger but poorly delineated Mare Fecunditatis.

moon antares

Keywords: Astronomy news, Antares, lunar occultation