EYES ON THE NIGHT SKY: OCTOBER 2017
This month, the nights really start to draw in, so take those opportunities after dinner to wrap up warm, get out there and explore the night sky. Astronomical darkness will occur at around 8pm in the middle of the month, which means that the Sun is low enough below the horizon (below 18 degrees) not to cast its light into the night sky. This is an opportune time to study more distant and dimmer objects, and see our favourite celestial objects in more detail. This article and future ones will provide interesting targets and sky maps for those who have small and large telescopes, a pair of binoculars, or even a pair of eyes!
Becoming familiar with the night sky is an exciting adventure and there are plenty of excellent books, apps and software you can use. For free software, many people have found Stellarium to be a good visual resource for learning about the Constellations and the positions of celestial objects such as nebulae, planets and much more. Skeye is another free app for smart phones and tablets which shows a live sky map according to where you hold your device. For books, Sky and Telescope's Pocket Sky Atlas has been popular amongst visual observers and can be found in most main book retailers online.
For those who are going out for the first time, allow your eyes to become dark adapted and try to get away from sources of light pollution, such as street lights, houses, etc. – dark adaption takes around twenty to sixty minutes. In the meantime, you can enjoy scanning the skies and take in the majesty of the Milky Way emerging as your eyes adapt. You’ll still be able to see it this time of year as it sets westwards – Mid October would be the end of the optimum time to see it.
The constellation Andromeda (above) will be riding high in the sky this time of year from 10pm with the Andromeda Galaxy (M31, the green circle on map) positioned near the Zenith. In all rural and most rural/urban skies, you will be able to see it with the naked eye – take a look at the map and study the Pegasus and Andromeda constellations; the Andromeda Galaxy is labelled. Through a pair of 10x50 binoculars, it looks like a fuzzy elliptical shape with a brighter core. Through a Newtonian telescope of eight inches aperture, you can resolve two dark dust lanes. This wonderful galaxy contains 1 trillion stars – twice as much as our Milky Way galaxy and is 2.5 million light years from earth. With a low power eyepiece, you can spot nearby galaxies M32 and M110.
Fortunately, the stunning summer Constellation of Cygnus (above) is still in the sky, although it starts to set in the West around 3am in the morning. 9:30 pm would be a good time to try and find a breath-taking double star called Albireo (the green circle on map), the fifth brightest star in this constellation. To the naked eye, it glints as a single white star but through a telescope from two inches of aperture and upwards, that single star splits into two; one almost royal blue in colour and the other, brilliant citrus orange! It seems the vibrancy fades with much larger apertures of fourteen inches and upwards, so this is a special one for those smaller telescopes!
If you have a pair of 10x50 binoculars handy, Comet C/2017 O1 ASASSN is approaching perihelion – closest proximity to the Sun - and during October it may become bright enough to be seen through binoculars or small telescopes. It is riding high between the constellations of Perseus and Auriga.
Next, a pleasing planetary conjunction for the eyes only, if you are willing to get up early. Venus and Mars come together in the dawn twilight during the first half of the month, until 5thOctober from 5.00am; Venus passes just twelve minutes of arc north of Mars around 5:50am (best seen the mid Pacific regions!). Meanwhile, in the UK, see them close on the mornings of 5th and 6th October. The waxing crescent Moon passes close above Mars on the early dawns of 17th October and of Venus on 18th October
On 19th October, the planet Uranus will be at opposition. Now is the best time of year to observe it as this blue/green planet will be at its brightest, being fully illuminated by the Sun and positioned at the closest approach to Earth. Owners of eight inch telescopes and above will be able to study this planet which will resolve as a blue/green disk. Its moons can be spotted with careful observation, steady skies and a twelve inch telescope.