The March Sky
The March Sky
The speaker opened with the planetary scene, showing some of the superb results obtained by Eric Ng in Hong Kong, directing a Philips ToUcam webcam CCD at Jupiter. Ng had imaged a white oval passing the Great Red Spot on February 17 – an event also sketched by Dr Richard McKim – as well as the transit of Io on March 13, with the planet's shadow well-resolved. Many of those amateurs with sufficient resolution had watched with interest on January 28 as white spot Z, nicknamed "barge killer", had approached barge B1. Images of the event by Damian Peach featured a number of smudges within the North Temperate Belt – past victims of Z. In this instance, however, B1 was to receive light treatment.
Closer to home, Mars already subtended 7" at the time of the meeting, and would peak at 28" at opposition on August 28. The most favourable declination would be -13° in mid-July. Syrtis Major was recommended as one of the most distinctive surface features to watch out for.
In the comet scene, C/2002 V1 (NEAT) had passed within 0.1 AU of the Sun at perihelion on February 18. This was sufficiently close that there had been a significant risk of it becoming engulfed by a solar flare. Whilst the comet had clearly not been observable by amateurs, the Soho solar coronograph had provided a superb view, and the speaker predicted it would have appeared at mag 2 at perihelion. Meanwhile, Juels Holvorcem was presently passing through Andromeda at mag 7, but would plunge into twilight in early April. C/2001 HT-50 (LINEAR-NEAT) was in Orion at around mag 11-12. Mr Mobberley suggested that CCD observers might like to take advantage of an excellent test of the dynamic range of their equipment on March 21, when it would pass within 8' of Betelgeuse. C/2002 X5 Kudo-Fujikawa was back, low in the southwestern twilight of Orion at mag 9. On March 9 it would skirt past Rigel, before a close encounter with the Orion Nebula (M42) on April 10.
Tom Boles had had an illustrious month, discovering 11 supernova events since the previous meeting. As at February 13, Boles had had 38 supernovae to his name, as compared to Armstrong's 40. But, Boles had since added three further events to his total, making him the UK's undisputed leader in supernova discovery. The UK amateur total was now 90, and it seemed highly probable that the 100th event would come before the close of 2003. Mr Mobberley reflected upon how inconceivable such a suggestion would have been only five years ago. For minor planet observers, asteroid Vesta would be passing through a dense cluster of galaxies in Virgo until mid-July, maintaining a brightness around mag 6-8.
Mr Mobberley reminded members of the ongoing series of Multiple Galilean Events of the Jovian moons. January 17/18 had seen five simultaneous transit events on Jupiter's surface, and whilst the weather had been a mixed bag, observers in East Anglia had fared best. Damian Peach had sent characteristically clear images of the transits from Tenerife. Favourable events in the near future included March 20, when Io would occult Europa between 23:51 and 23:54UT to a maximum of 59%; March 24, when Io would eclipse Ganymede between 21:59 and 22:05UT to a maximum of 9%; and March 25, when Europa would occult Ganymede between 20:45 and 20:52UT to a maximum of 28%.
May 7 would see the first solar transit of Mercury since 1999, with greatest transit at 7:52UT. Each century sees an average of 14 such events, mostly in November (perihelic), but occasionally in May (aphelic). A second transit of Mercury would take place on 2006 November 8-9, with rarer transits of Venus on 2004 June 8 and 2012 June 5-6.
There would be a total lunar eclipse on May 16, visible from the UK at moonset with an altitude of only 10° above the SSW sky. Members able to observe at such altitudes were advised to watch out for the spectacular red colouring of the eclipsed Moon. An annular solar eclipse would be visible from Scotland on May 31, with the remainder of the UK witnessing a partial event. This was the UK's first annular eclipse since 1921, and the last until 2093. Mr Mobberley explained that annular events were possible because whilst the Sun only varies in angular size between 31'31" and 32'25", the Moon varies between 29'22" and 33'31". Thus, there are times when the Moon is not sufficiently large as to be able to entirely eclipse the Sun, and a ring of sunlight is left around its silhouette. On the occasion of May 31, both objects would be close to their smallest possible sizes.
Following the applause for Mr Mobberley's well-illustrated presentation, the President invited Dr John Mason to introduce a series of eclipse reports from members who had viewed the total solar eclipse of 2002 December 4 in southern Africa and Australia.