Looking Forward, the Planets in October and November2018

Mercury was in superior conjunction in late September so is moving into the evening sky at the start of October but gives a very poor apparition for the Northern Hemisphere. Greatest Eastern Elongation occurs on the 6th of November with Mercury sitting 23 degrees east of the Sun but at such a low elevation from the UK it is barely above the western horizon at sunset. During the last week of October Mercury sits very close to Jupiter; since Jupiter is relatively easy to find in daylight it might be used as a marker to find Mercury as long as all precautions are taken to keep the Sun out of the fields of view. On the 27th of November Mercury moves between the Earth and the Sun (inferior conjunction).

Venus sits very low to the western evening horizon in early October and is unobservable in darkness from UK latitudes. The planet also moves into inferior conjunction, on the 26th of October, so starts to appear in the morning sky after this. It becomes obvious just before dawn from the end of the first week of November and will improve throughout the month. By mid-November Venus rises nearly two and a half hours before the Sun and reaches nearly 20 degrees of elevation by sunrise. Even accounting for atmospheric extinction-effects Venus will shine brighter than magnitude -4 and will be a magnificent sight sitting very close to the star Spica for the rest of the month.

As darkness fall in early October, Mars becomes visible low in the south-east and transits, due south, around 2000 UT. Initially Mars is still low at transit, around 15 degrees above the horizon for mid-UK latitudes, however elevation improves night on night and by early November elevation is above 20 degrees transiting at 1900 UT and by month’s-end this is just less than 30 degrees at 1815 UT. Brightness falls from magnitude -1.3 to 0.0 and apparent size from 16 arcseconds to just under 10 in the period meaning that there is still plenty to see here, especially with the improved elevation in British skies.

At the start of October Jupiter may be seen fleetingly, very low in the south-west shortly after sunset but is soon lost as the period progresses; moving into conjunction, behind the Sun on November 20th. It is a potential daytime target, especially during October but, I must stress, it soon gets dangerously close to the Sun and the risk of permanent eye damage is very real when trying to find it. A well aligned mount with accurate go-to capabilities can be reasonably safe and Jupiter responds well to daylight imaging with an infrared band filter but Do Take Care.

It is a similar story for Saturn however that planet can at least be seen from twilight and on into full darkness, low in the south-west from the start of the period shortly after sunset. By November Saturn itself sets around 1930 UT and by 1555 UT at the end of the month so is best seen in early October or, like Jupiter, with care in daylight.

Uranus is very well placed for observation all night in this period as it is at opposition on the 24th of October. Its south-transit times (UT) are 0126 on 1st Oct; 0030 on 15th Oct; 2316 on 1st Nov; 2219 on 15th Nov and 2117 on the 30th. Throughout the period Uranus is at nearly 50 degrees of elevation as it transits. At magnitude +5.7 and 3.7 arcseconds in size it may be seen by the naked eye from a dark site, close to the border between Cetus and Pisces, but is best seen telescopically. It can be distinguished from the background stars as it appears distinctly blue-green, a very odd colour for a star, and at low magnification will look slightly unfocussed compared with the true stars surrounding it; higher magnification will reveal its disc. Larger aperture telescopes and suitable monochrome planetary cameras using infra-red filters may reveal cloud features on this distant world while colour cameras may show banding or shading from equator to pole.

Similar equipment may reveal clouds on Neptune if the seeing conditions are good however Neptune is past opposition so is now transiting well before midnight and should be observed before Uranus. Find it just under 3 degrees east of the star Hydor in Aquarius in early October, reducing to 2 degrees east by the end of the period. At Magnitude +7.8 and 2.4 arcseconds in size Neptune is a telescopic object only but shows a jewel like azure-blue colour and is worth seeking out. Imagers who capture detail on either of the ice giants should try to also capture an identifiable moon of either planet within the image as this allows very accurate timing of the image and therefore determination of the position of clouds and subsequently of atmospheric drift rates.

Alan Clitherow