BAS - Monthly Sky Guide

Transcription

1 BAS - Monthly Sky Guide August 2018 In the early evenings of August we will have the centre of our Milky Way Galaxy stretching right across the sky from the south-west to the north-east. Most of the best observing targets will be high in our southern sky. A great time to explore the centre of our galaxy for nebulae, globular clusters and dense star clouds. 1

2 Dark Sky Best Observing Dates - August Best observing dates You will need to have your heavy coat and gloves ready this month. New Moon is Saturday August 11 th, so the best Moon-free observing nights will be from about So August 5 th the 12 th On the 5th the moon rises after midnight and rises later each night through until New Moon on the 11 th. On the 12 th you will need to wait until 7:00pm for the Moon to set and dark-sky conditions. 2

3 Useful Telescope Alignment Stars Alignment Stars: Arcturus Vega Arcturus in Bootes Vega in Lyra These might not be the best stars for aligning your telescope, due to the somewhat low position in the sky, but they are good to learn. Arcturus will be the brightest star in the low north-west sky and is distinctly yellowish in colour, and so difficult to mistake for another star. Vega is low in the northern sky and the brightest star in its vicinity. The distinct shape of the constellation Lyra, a parallelogram slanting off to the east and above Vega, helps ensure you have properly identified Vega. Just the brightness of Arctuturs and Vega, respectively the 4 th and 5 th brightest stars in the entire sky, should make them easy to identify and find in the finderscope and eyepiece. 3

4 Constellation of the month - Lyra Observing targets: Messier 56 globular cluster Messier 57 planetary nebula Lyra constellation lies in the low northern sky. It represents the lyre, a small harp style of musical instrument. The constellation is associated with the myth of the Greek musician and poet Orpheus and was first catalogued as a constellation by the Greek astronomer Ptolemy in the 2nd century. Orpheus was known for his ability to charm even stones with his music, for his attempts to save his wife Eurydice from the underworld, and for being the harpist and companion of Jason and the Argonauts. In Greek mythology Orpheus was killed the followers of Bacchus, the god of agriculture and wine. (Perhaps alcohol was factor in the crime.) When he died, his lyre was thrown into a river. Zeus sent an eagle to get the lyre and placed both of them in the sky. Messier 56 is a globular cluster approximately 32,900 light years distant from the solar system. The cluster is about 84 light years across. It was discovered by Charles Messier on January 19, The Ring Nebula, Messier 57, is a famous planetary nebula in Lyra constellation, located south of the bright star Vega. It is relatively easy located between two moderately bright stars just south and east of bright star Vega. The nebula was 4

5 formed when a shell of ionized gas was expelled by a red giant star that was in the process of becoming a white dwarf. It is expanding at the rate of about 1 arc second per century. The central planetary nebula nucleus (PNN) was discovered by the Hungarian astronomer Jenő Gothard on September 1,

6 The Planets Jupiter Saturn Mars West August is still an excellent month for observing Jupiter, Saturn and Mars, however time is running out for Jupiter as it heads for the western horizon. Venus is also visible for a short period in the low western sky just after sunset. All the other planets are past oppositions and gradually diminishing in size. However, early to midevening will still be a great time to observe Saturn as it will be high in the sky near the meridian and viewed with the least atmospheric distortion. 5

7 Norma Hercules A couple of constellations in the sky along the meridian at about 9 PM during the New Moon period are the constellations Norma and Hercules. The two constellations are vastly different to each other. Norma is in the southern sky and its name means normal in Latin (referring to a right angle) and it represents a level, a set square, a rule, or a carpenter s square. The constellation was introduced by the French astronomer Nicolas Louis de Lacaille in the mid-18th century. Norma is one of the smaller constellations and does not have any prominent stars. Hercules is in the northern sky and is a large constellation with some reasonable bright stars marking the constellation asterism. In mythology, the constellation Hercules is usually associated with the penultimate labour of Heracles, which involved killing the dragon Ladon, who guarded the garden of the Hesperides. The dragon is represented by the constellation Draco. Hercules constellation was first catalogued by the Greek astronomer Ptolemy in the 2nd century. 6

8 Norma Open Cluster NGC 6067 Norma is lacking the rich cluster of galaxies and show-stopper objects of nearby constellations. Perhaps the easiest deep-sky object to observe in Norma is the open cluster NGC The star Kappa Normae lies on the longest arm of the constellation and open cluster NGC 6067 is very close and a little to the north to this star and both objects are likely to be within view in a wide angle eyepiece. The cluster has an apparent magnitude of 5.6 and is 4,621 light years distant from Earth. It is 12 in diameter and can be easily be seen with binoculars or a small telescope. 7

9 Hercules M13 Hercules has everything Norma lacks, and in abundance. Perhaps the most well known object in Hercules is Messier 13, also known as the Hercules Globular Cluster. This globular cluster consists of about 300,000 stars, in a sphere approximately 145 light years in diameter and located 22,200 light years distant from our solar system. The Hercules Globular Cluster was discovered by the English astronomer Edmond Halley in 1714 and included in Messier s catalogue as Messier 13 on June 1, The cluster can easily be seen in small telescopes. Many further hours can be invested in Hercules seeking its abundant galaxies. 8

10 Build your own observing list Click Find Objects Select object types Select constellation Search 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 can generate a fantastic observing list of object types you are interested in. 9

11 Avoiding clouds More info: 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