The Steavenson Award


The 2003 Martian Apparition

Dr McKim opened with his own experiences of trying to image the Martian moons. The moons were sufficiently faint that a moderately large aperture was required for them to be detectable, and an occulting bar blocking the glow from Mars might be necessary. However, the speaker had seen Phobos and Deimos very easily with the 1-metre Cassegrain on Pic du Midi, and without an occulting bar!

Mars would be at perihelic opposition on August 28, but this year's apparition was already well under way, and the speaker had started his own programme of observation in January. At this time, it was only 4 arcseconds across. At opposition it would be at declination 16° south, and some 25 arcseconds across. Dr McKim urged observers not to wait until opposition to start observing. The previous apparition of 2001 (at the start of southern spring) had coincided with a planet-encircling dust storm, effacing all surface detail for several months.

The speaker showed some of the images which had been received of the 2003 apparition by the Section at the time of the meeting. These included a number of Dr McKim's own sketches, which were, as always, drawn with superb precision and of great artistic beauty. Don Parker's CCD images were also notable, and the speaker took the opportunity to congratulate him on his well-deserved Steavenson Award. Amongst the clearly visible surface features were Syrtis Major; the Hellas impact basin, currently with a dull appearance; and Solis Lacus, a dark eyeball-like spot. The latter had been close to the origin of a small dust storm in May, but the spread of dust had come to a rapid halt. In the same month, the southern polar cap had begun to break up, revealing some interesting surface details.

Dr McKim displayed some images by Eric Ng, and others, taken with the same model of the Philips ToUcam Pro webcam which Mr Mobberley had praised earlier. This camera had recently become increasingly popular among the section's CCD observers. The speaker had found that whilst the webcam produced excellent red and green images, the blue images were not directly comparable with those of other cameras unless subjected to further selective filtration.

The speaker's own programme presently involved getting up at 3am as often as possible to make pre-dawn observations whenever the weather permitted. Recently, the conditions had often been favourable, with Mars high enough in the sky to make good observations around half an hour before dawn. The seeing was often good, but usually deteriorated rapidly towards sunrise.

The Martian year was now significantly past the date when the 2001 planet-encircling storm had erupted, and Dr McKim believed that historical precedents placed the chances of a similar storm at this opposition at one-in-three. During the spate of such storms in the 1970s, there had often been planet-encircling dust storms in two successive Martian years, but never in more than four successive years.

Dr McKim closed by urging all BAA members to make observations of Mars this year, and preferably to start as soon as possible.

Following the lengthy applause for Mr Mobberley and Dr McKim's presentations, the President adjourned the Ordinary Meeting until the Association's Out of London Meeting, to be held in York on September 5. The meeting was followed by four short talks by Association members, and Neil Bone commenced by reviewing the meteor activity of 2002-3.






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