BAS - Monthly Sky Guide

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1 BAS - Monthly Sky Guide September 2018 In the early evenings of September the centre of our Milky Way Galaxy stretching across the western sky and is heading for the horizon. Now is a good time to explore deep space beyond our Milky Way and seek objects in lesser observed constellations and galaxies at unimaginable distances but within reach of our small telescopes. 1

2 Dark Sky Best Observing Dates - September Best observing dates The days are getting a little longer now and the nights shorter. New Moon is Sunday September 9 th, so the best Moon-free observing nights will be from about September 3 th to the 11 th. 2

3 Useful Telescope Alignment Stars Scorpius Piscis Austrinus Alignment Stars: Antares Fomalhaut West East We have recommended Antares a number of times as an excellent alignment star as it is bright, easy to find in Scorpius and distinctly orange in colour and therefore hard to mistake for another star. However, Fomalhaut is a bit harder to find, even though it is the 18 th brightest star in the sky, and the brightest star in that part of the sky. The fact that Antares is in the western side of the sky and Fomalhaut is in the eastern sky also makes them good to use together as alignment stars. 3

4 Constellation of the month - Pavo Observing targets: Globular Cluster NGC 6752 Galaxy NGC 6744 NGC 6752 Pavo constellation lies in the southern sky and is named for the peacock in Latin. In Greek mythology, the peacock was Hera s sacred bird. The goddess drove through the air in a chariot drawn by peacocks. The constellation was introduced by the Dutch astronomer Petrus Plancius from the observations of Dutch navigators Frederick de Houtman and Pieter Dirkszoon Keyser in the late 16th century. NGC 6752 is a globular cluster. It is the third brightest globular star cluster in the night sky, fainter only than 47 Tucanae (NGC 104) in the constellation Tucana and Omega Centauri (NGC 5139) in Centaurus. The cluster has an apparent magnitude of 5.4 and is about 13,000 light years distant from our solar system. NGC 6744 is an intermediate spiral galaxy in Pavo. It has an apparent magnitude of 9.14 and is approximately 31 million light years distant. It is one of the most similar nearby galaxies to the Milky Way. NGC 6744 has at least one satellite galaxy, the distorted NGC 6744A, which bears a passing resemblance to one of the Magellanic Clouds, irregular dwarf galaxies in the Local Group. 4

5 The Planets Neptune Mars Saturn Jupiter West The planets we have been observing for months are all now the western part of the sky in the early evening. Jupiter in particular is now heading low in the sky towards the horizon time is running out. However there is still time to observe Saturn and Mars however they are now well past opposition and their discs are getting smaller and smaller each day. Catch them while you can. In this month we also have the planet Neptune at opposition, so try your luck at finding this beautiful pale blue dot in Aquarius. 5

6 New Moon - 9 PM meridian constellations Capricornus Indus The Capricornus constellation named for the goat in Latin and is located in the southern sky on the ecliptic path followed by the wandering planets. Capricornus is one of the 12 zodiac constellations however it is also one of the faintest constellations in the sky. Like other constellations of the zodiac, Capricornus was first catalogued by the Greek astronomer Ptolemy in the 2nd century. The constellation is associated with two mythical creatures from Greek legends: the deity Pan and the goat Amalthea, who suckled Zeus when he was very young. Capricornus constellation is home to the famous globular cluster Messier 30. Indus is a relatively dim constellation located in the southern hemisphere. It does not contain any bright stars and is difficult to identify in light polluted skies. The constellation represents the Indian, referring to a native of either of Asia or the Americas at the time the constellation was created by the Dutch astronomer Petrus Plancius in the late 16th century. Indus does not have any bright objects to observer, however, it does have a sprinkling of galaxies that are worth seeking out. 6

7 Capricornus Globular cluster M30 Messier 30 is a globular cluster approximately 28,000 light years distant and about 90 light years across in size. It is easy to observe even in small telescopes. The cluster is approaching us at the speed of km/s. It was one of the first deep sky objects discovered by Charles Messier in M30 is a relatively dense cluster and many of the brightest stars in the cluster are magnitude 12 red giants. Like Messier 15, Messier 70, and many other globular clusters in the Milky Way Galaxy, M30 has undergone a core collapse. Its core is now only 0.12 arc minutes in size, and half of the cluster s mass is contained in a spherical radius that is 17.4 light years across. 7

8 Indus Galaxy NGC 7090 Galaxy NGC 7049 If you have a dark sky it is worth trying to observe some of the galaxies in Indus. A good target to start with is NGC 7049, a galaxy located about 100 million light years from Earth. The galaxy is larger than our Milky Way and spans approximately 150,000 light years. It has a prominent dust ring and relatively few globular star clusters. It has characteristics of both a spiral galaxy and an elliptical galaxy. The galaxy s unusual appearance is believed to the result of several recent collisions with other galaxies. You might also try finding NGC 7090, a spiral galaxy in Indus. It has an apparent magnitude of and is about 30 million light years distant. It was discovered by the English astronomer John Herschel on October 4,

9 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

10 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