BAS - MONTHLY SKY GUIDE October 2018 The early spring nights of October mean it is time to look beyond our Milkyway Galaxy into deep space in search of distant galaxies. 1
DARK SKY BEST OBSERVING DATES - JULY From about Wednesday October 3 rd the moon does not rise until after midnight. This will provide plenty of evening observing time until just after the New Moon on October 9 th when the Moon once again impinges on the early evening sky. So, October 3 rd to 10 th looks best this month. 2
USEFUL TELESCOPE ALIGNMENT STARS Altair Alignment Stars: Altair in Aquila Achernar in Eridanus Achernar Achernar and Altair are the 9 th and 13 th brightest stars in the entire sky. However, in October they are two of the brightest stars in the evening sky and well placed for use as telescope alignment stars. Achernar is in the southern sky at the southern end of the constellation Eridanus, the river. Look for it as the brightest star in the sky a little to the east of the Small Magellanic Cloud. Altair is in the north-western sky in the constellation Aquila, the eagle. It helps if you can learn to recognise the cross-like shape of Aquila that somewhat suggests the shape of a bird with outstretched wings. Altair might represent the eye of the eagle. 3
CONSTELLATION OF THE MONTH - CAPRICORNUS Observing targets: Messier 30 Jellyfish Cluster Mars M30 The constellation Capricornus the Sea Goat is one of the constellations on the ecliptic path and this month is host to the planet Mars. The constellation is one of the faintest and is not easy to discern. However, this month Mars provides a great beacon for locating the constellation even if you cannot see all of its main stars. The constellation was identified in many ancient civilizations but the Capricornus name was confirmed as one of the original 48 constellations defined by the Greek astronomer, Ptolemy, around the second century of the current era. The Sea Goat myth is attributed to a creature that lived in the ocean, but near the shore, that was half goat and half fish. These creatures were intelligent and could speak and think for themselves. The myths are many and convoluted. Apart from Mars this month, the easiest object to observe in Capricornus is the globular cluster Messier 30, the Jellyfish. The cluster is about 22,000 light years from Earth and contains about 160,000 solar masses. 4
THE PLANETS The focus is Mars and Saturn Neptune Mars is in Capricornus Saturn is Sagittarius Neptune is high in Aquarius Mars Saturn All the planetary action this month is in the western sky as the planets slowly depart our sky and head towards conjunction with the Sun in the coming months. Mars is still bright and well placed high in the sky for observing. Saturn is getting a little low in the sky and obscured by our atmosphere. However, Neptune is now high overhead in Aquarius and worth seeking out. Look for a distinctly pale blue dot, or tiny disk, and wonder at its lonely location 29 astronomical units, or over 4.3 billion kilometres, from Earth and your little telescope mirror or lens. 5
NEW MOON - 9 PM MERIDIAN CONSTELLATIONS Aquarius Piscis Austrinus A couple of constellations in the sky along the meridian at about 9 PM during the New Moon period are the constellations Aquarius and Piscis Austrinus. Piscis Australis was first catalogued by Ptolemy in the 2nd century, but its history dates back to Babylonian times. This is one of the smallest and faintest constellations with few dark-sky objects, however, it does boast the star Fomalhaut, the 18 th brightest star. In 2008 this was the first stellar system with an exoplanet to be imaged in visible wavelengths. The image showed a tiny dot, the planet Fomalhaut b, embedded in a vast disk of dust and matter orbiting the central star. Aquarius lies in a region of the sky sometimes referred to as the sea due to the number of constellations associated with water Aquarius, Pisces, Eridanus, and Cetus and others. 6
AQUARIUS M2 Helix Atoms for Peace Aquarius has lots of interesting deep sky observing targets. An easy object is the globular cluster M2 located about 37,500 light years away and containing about 150,000 stars. The Helix Nebular requires a dark sky to be seen at its best. This is a large planetary nebular, nicknamed The Eye of God, located 750 light years away. The gas shells around the dying central star provide a glimpse into the future as to how our Sun might look in another 5 billion years or so. You might also try and observe the Atoms for Peace Galaxy, catalogued as NGC 7252, is a peculiar elliptical galaxy, approximately 220 million light years distant. It is believed to be the product of a collision between two disk galaxies roughly a billion years ago. 7
PISCIS AUSTRINUS NGC 7314 NGC 7173 Observing in Piscis Austrinus is pretty much confined to galaxy hunting. A challenging and interesting target is NGC 7173, an elliptical galaxy of apparent magnitude 11.9 located about 114.8 million light years distant from the solar system. It was discovered by the English astronomer John Herschel on September 25, 1834. This compact object consists of three galaxies, two of which are large ellipticals, in the early stage of merging into a single massive galaxy. You might also try hunting for the spiral galaxy NGC 7314 located about 66 Mly away. This is a large face-on spiral that can be observed in a dark sky by telescopes with an aperture of 6 inches or more. 8
BUILD YOUR OWN OBSERVING LIST Click Find Objects Select object types Select constellation Search https://dso-browser.com/ Make sure you take a look at the great observing planning tool DSO-Browser before the New Moon period. This is a fantastic tool to help you build a list of objects you can try and find each month. Just a few clicks on www.dso-browser.com can generate a fantastic observing list of object types you are interested in. 9
AVOIDING CLOUDS www.cloudfreenight.com www.skippysky.com More info: http://philhart.com/content/cloud-forecasts-australian-astronomers And the find the best cloud-free evenings for observing make sure you check CloudFreeNight and Skippysky as you plan your next observing evening. 10