A coincidence of rare events last night. Just after midnight, an hour or so after the start of heavy snowfall in Beijing (an event that occurs only a handful of times every year, despite very cold winters), there was a loud rumble seeming to come from the east. It was so odd that I went outside, and it continued for what seemed like a couple of minutes. Having returned indoors, I saw a bright flash through the curtains followed immediately by an explosive clap of thunder. A few minutes later another long rumble, seeming to come from the west, and then it was over -- even as the snowstorm continued (the temperature seemed just about or slightly above freezing, at a guess). Wikipedia has an interesting entry on the phenomenon which confirms how rare it is. The conditions that normally seem to trigger this -- proximity to the sea or large lakes, doesn't seem to apply here. Beijing is about 150 miles from the sea. Snow this early in the year is also highly unusual, although there was an exceptionally early snowfall on Nov 1. The local media said the thunderstorm was the latest in Beijing in 150 years. Beijing has experienced thundersnow before, however, as recently as 2003.
Strangely Astromist on my Pocket PC failed to predict it, but Calsky did with great precision -- the emergence of Europa from Jupiter's shadow. I don't recall having witnessed this common event before from start to finish. Jupiter was quite low in the sky, over an apartment building in terrible seeing. The ending of the eclipse of Europa appeared to take half a minute or so, from a very faint point of light to sixth magnitude. The Great Red Spot was supposed to be crossing Jupiter's face at that time, but I couldn't make it out. A 15mm Super Plossl was the maximum the planet could sustain.
Sunspot 1029, unusually large and just unusual for being a spot on a normally -- these days -- spotless sun, was very prominent near the western limb close to sunset. This is my mirror image sketch, drawn around 0800 gmt on Oct 29 using a 15mm Super Plossl.
I got my directions mixed up until I found this useful explanation of how it works from http://the-moon.wikispaces.com/IAU+directions:
Like the Moon, early maps of the Sun were drawn with the limbs marked according to which horizon on Earth they faced (or, equivalently, their directions on the celestial sphere. The convention for solar mapping has never been changed: professional astronomers continue to describe active regions on the Sun as appearing on the "east" limb, rotating across the Sun's face, and disappear over the "west" limb. But this means they are moving from the Earth's east to the Earth's west. And following a tradition dating back to the 1850's, longitudes on the Sun are numbered (as they still are on the Moon) increasingly positive towards the Earth's western horizon (although a full 0 to 360° system is used). Since the 1961 change in the lunar mapping convention, the Sun is the only solar system body for which a north-up map will have "east" on the left.
A hazy night with thin cloud, with the moon and nearby Jupiter all I could see. Attached is a sketch of the moon's southern limb drawn between 1300 and 1400 gmt on Oct 27. The large crater at the bottom is Clavius (last sketched a couple of years ago, see http://www.astronomyblogs.com/member/northandeast/?xjMsgID=37697). The other large features are Crater Maginus, above and to the left of Clavius, and Tycho with its prominent central mountain at the top.
... will be less than three degrees apart in the evening of Tuesday Oct 27 in northern China.
