Starwatch: The October night sky

Our October nights bring a rich procession of stellar interest that ranges from the Summer Triangle, high on the meridian at nightfall, to Orion and his blazing retinue of winter companions in the S before dawn. It is just a pity that most of the bright planets are poorly placed near the Sun's glare. The latter certainly affects Venus which, from our latitudes, sets only five minutes after the Sun tonight as it approaches inferior conjunction on the Sun's near side on the 29th. Mars, too, has been swallowed up by our evening twilight. Jupiter, though, reached one of its closest and brightest oppositions last week and continues to rule our nights. Conspicuous at mag –2.9, brighter than any star, it climbs from low in the E at nightfall to pass some 30° to 35° high in the S about 80 minutes after our chart times, and then sinks to set in the W another six hours later. It lies to the S of the Square of Pegasus where it edges 3° west-south-westwards to cross from Pisces into Aquarius. Telescopically, Jupiter appears 48 arcsec across when close to the Moon on the 19th/20th. Mercury is nearing the end of its best morning apparition of 2010. Bright at mag –1.1, it stands 6° high in the E only 30 minutes before sunrise on the 1st, but drops out of sight over the following few days. Saturn emerges from our morning twilight at mid-month. By the 31st, it rises by 04:30 GMT and is obvious at mag 0.9 low down in Virgo in the ESE before dawn. There is a chance that Comet Hartley may become a diffuse naked eye object as it passes close to the Earth and sweeps from Cassiopeia to Gemini during October. More certain is that the red pulsating variable star Mira in Cetus is brightening to a maximum in mid-October when it may reach mag 3 or 4. October diary 1st 02h Saturn in conjunction with Sun; 05h Last quarter 7th 20h New moon 10th 03h Moon 4˚ S of Mars 14th 22h First quarter 16th Variable star Mira at peak brightness 17th 02h Mercury in superior conjunction 20th 12h Moon 7˚ N of Jupiter 23rd 03h Full moon 29th 02h Venus in inferior conjunction 30th 14h Last quarter 31st 02h BST = 01h GMT End of British Summer Time * Times are BST