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Ant

Sky Guide for September 2007

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This is the first (hopefully of many) SGL monthly guides. Please use it however you want - a PDF version will be available in a few days. I'd like to thank Ian (lunator) for all his help with the double star information. If any one has idea's/suggestions please let me know.

Ian has already suggested that not everyone has a good east facing garden (I have and assume that everyone has), so from next month we'll be picking a constellation in the East and one in the west.

Ant

Sky Guide for September 2007.

Planets. ALL TIMES GIVEN ARE GMT.

Mercury, is an evening star at the moment. Even though it reaches maximum eastern elongation on the 26th it will still be too low to see.

Venus, is a morning object. It is, as usual, very bright at magnitude -4.5. At the beginning of the month it rises around an hour before the sun but at the end of the month is rises a full 4 hours before the sun.

Moon

Last Qtr 4th

New Moon 11th

First Qtr 19th

Full Moon 26th

Mars, is magnitude 0 in Taurus – it’s rises by around 9pm at the end of the month. The moon is close by on the 4th.

Jupiter, is magnitude -2 in Ophiuchus and just above Antares. At the end of the month it’s setting by 8pm. The moon is below on the 18th.

Saturn, is in Leo. Rising by 2:30am at the end of the month. Moon close on the 10th.

Uranus, is at opposition on the 10th September. It will be setting by 4am at the end of the month. The moon will be close by 25th.

Neptune, setting at the end of the month by 1:30. Moon nearby on the 23rd.

Constellations

Cassiopeia.

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(click to enlarge)


LEGENDS of CASSIOPEIA

Cassiopeia: one of only three female figures in the northern skies. This constellation is one of the circumpolar constellations visible at about 40° north latitude. Its legends often reflect the fact that the constellation never sets below the horizon.

Greek: she was the vain and beautiful Queen of Philistia, sometimes referred to as Ethiopia. Claiming to have beauty that rivaled the Nereids, her punishment was the sacrifice of her daughter, Andromeda, to the sea monster Cetus. After her daughter was saved and promised to Perseus as his wife, Cassiopeia plotted with her daughter's fiancée Agenor, to kill Perseus. While outnumbered and attacked at his wedding feast, Perseus pulled Medusa's head from his bag and transformed Cassiopeia, Agenor and his men to stone. The Queen and King Cepheus are depicted in the sky facing each other's feet. They cannot speak to each other. Because the Queen insulted the sea nymphs, the pair never set below the surface of the sea. The constellation's name is derived from a Phoenician phrase that means the Rose-Colored Face.

Assyria: she is the Mistress of Grain depicted with a palm frond or grain in her left hand. This agricultural tie brings the constellation close to the mythologies of Virgo.

Arabic legend: known as Kaff al-Habib, the dyed hand, the constellation was eventually considered to be the hand of Fatima, the daughter of Mohammed.


The 5 main stars that make up the "W" of Cassiopeia make this circumpolar Constellation almost unforgettable.

? Cassiopeiae, "Schedir" is a magnitude 2.42 star (absolute magnitude 0.1). It's a giant with a spectral class is K0 and lies at around 163 Light Years.

? Cassiopeiae, "Caph" is a magnitude 2.42 star (absolute magnitude 1.6) - this places this star much closer to us than ?). Caph is a dwarf star with a spectral class of F2. It is 47 Light Years from Earth.

? Cassiopeiae, "Cih" is a giant star with a spectral class of B0. Cih is a variable star ranging from Magnitude 1.6 to 3.0. Cih is 650 light years distant.

? Cassiopeiae, "Rucbar or Ksora (knee I think)" is a magnitude 2.62 star (absolute magnitude of 1.0). It has a spectral class of A3 and lies at 76 light years from Earth.

? Cassiopeiae, "Segin" is another giant with a spectral class of BO, it's magnitude is 3.34 and lies at around 470 light years from Earth. Being this far means that the star has a absolute magnitude of -2.3.


The Milky Way runs through Cassiopeia which make this area of sky full of stars when observing with binoculars or a wide FOV scope. Having the Milky Way run through this constellation means that there are numerous open clusters (at least 26) and the famous Bubble Nebula (NGC7635). There are others...

As mentioned above there are numerous DSO's in Cassiopeia, here are

some of them.

M103, Open Cluster. A bright open cluster of around 175 stars set against the star-studded background of the milky way. M103 apparently looks like a Christmas Tree (but I can't see that myself). The cluster has many hot "Blue" stars and a couple of contrasting Orange / Red older stars. M103 is around magnitude 7 and 13 arc minutes in diameter.

NGC 457 (Owl Cluster), Open Cluster. Is a rich open cluster with nearly 100 stars. This cluster looks a little like ET (???, you couldn't make this up could you?). This cluster is big though and best viewed at low power - this cluster is 28 arc minutes in size (roughly the same as the full moon), lies at around 9000 Light years from Earth and is magnitude 6.4).

NGC 7789, Open Cluster. This cluster is around 1.6 billion years old. In fact it is one of the oldest clusters known to exist. NGC7789 is a spectacular cluster, it contains over 100 stars. The whole cluster is again around the size of the full moon. The brightest star in this cluster is magnitue 11. But the cluster has a magnitude of 6.7, making it a border line naked eye object from dark skies.

M52, Open Cluster. This cluster contains several hundred stars. The brightness of the cluster is magnitude 8 and this matched the magnitude of the brightest star. Strangly the brightest (orange) star isn't a member of the cluster - but happens to be along the same line of sight. The Bubble Nebula can be seen in the same FOV as M52(34 Arc minutes away), it is of Magnitude 11 and 15 Arc minutes in size.

Double Stars in Cassiopeia

Eta Cassiopeia STF60AB (24 Cass) RA: 0h49m05.10s DE:+57°48'59.0"

Magnitude: 3.52/ 7.36

A beautiful double star found between Alpha & Gamma Cassiopeia. First observed by William Herschel in 1779. Unlike the brightest stars in Cassiopeia this pair is a close neighbour of the Sun being less than 20 light years away. The colours attributed to this star have varied but they are usually yellow & Red/ orange. The primary is very similar to the Sun being G spectral class (classification varies from F9-G3) so as massive as the Sun but a bit brighter due to its age. It is believed to by much older at around 5800 million years old. The secondary is much dimmer being spectral class K7V. The pair currently around 13.0" with a PA of 319° (NNW) the orbital period is around 480 years.

Iota Cassiopeia STF 262Aa-B STF262Aa-C RA: 2h29m03.90s DE:+67°24'08.0"

Magnitude 4.63/6.92/9.05

This is an attractive visual triple star found by extending the line from delta through Epsilon and the same distance again. In smaller apertures and at lower magnitudes an easily split double is visible. If you push up the power then the primary is shown to be a tight double split by less than 3” and having a difference in magnitude of 2. The spectral classes of the 3 stars are A5/F5/G4 but most people see the Stars as white but there are reports of the Primary being yellow. The close visual pair has an orbit period of 840 years, all three stars are believed to be gravitationally bound and at the same distance of 160 light years. If you have a large scope 12” aperture then there is an even closer star to the Primary at 0.4”.

HR 9094 HD225009 STF3053 AB RA: 0h02m36.00s DE:+66°05'56.0"

Magnitude: 5.96/ 7.17

A colour contrast pair 5 degrees North of Beta Cassiopeia that is easily split at medium powers the pair being separated by 15” with the secondary at 70 degrees (ENE). The primary is a golden yellow and the secondary is a pale blue. The primary is a class G9 giant that has left the main sequence and is on the road to becoming a red giant. The secondary is an A class main sequence star. Given the separation it is unlikely that this pair is gravitationally bound, but they are still a visual treat with the added bonus that the stars are in the milky way so the field is full of background stars

HD11092 STF 163 AB RA: 1h51m16.90s DE:+64°51'17.0"

Magnitude: 6.80/ 9.13

A less striking colour contrast pair 1 degree North of Epsilon Cassiopeia. This is a wide pair separated by over 30” with the Secondary at 36 degrees (NE) The primary is a K4 super/bright giant with an obvious orange tint. The secondary is a B5 spectral class so can appear bluish.

This pair is an optical double with the Primary being considerably further away than the secondary.

Sigma Cassiopeia (8 Cass) STF3049 RA: 23h59m00.50s DE:+55°45'17.0"

Magnitude: 4.99/ 7.24

This is a tough double requiring at least an 8” scope and good seeing to cleanly split. The pair is between 2.5” & 3” with secondary being at 328 degrees ((NNW) with the brightness of the Primary overwhelming the secondary. The primary is blue/white of spectral Class B1V, the secondary is seen with various hues commonly green but is also a B class star. The pair is about 1500 light years away. First observed in 1780 by William Herschel, Struve noted the pair in 1830.

Perseus.

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Legends of Perseus.

Perseus is the cornerstone of probably the most intriguing and involved legends within classical Greek mythology. The bright, variable star Algol has often been identified as an evil star owing in part to its obvious changes in brightness every three days. Its name is derived from the Arabic Ras al-Ghul, the root of our word ghoul and translated as Head of the Devil. Strangely enough, later Christian representations of the constellation identified the star as the Bible as held by the apostle Paul.

Mesopotamia: associated with the violent, uncouth god Amurru or Martu. He is often described as a storm, one who digs up truffles in the foothills, eats raw flesh and has no permanent home. The nomadic people with which this god can be associated before he was absorbed into the mythologies of the ancient Mesopotamians are the Amorites described in the Bible.

A later representation marks this constellation as Marduk, who battled chaos in the creation of the universe and chained the goddess Istar (Andromeda) to a stone while preparing to fight her companion Tiamat (Hydra).

Greece: the legend of Perseus encompasses seven separate star groups including Cepheus, Andromeda, Cassiopeia, Pegasus, Cetus, Medusa (at one time considered a separate constellation) and of course, Perseus himself.

Abas the Invincible, king of Argolis, had two sons, Acrisius and Proetus, who quarreled continuously. Following their father's death, Proetus became infatuated with Acrisius' daughter, Danaë, which of course irritated his brother no end. They divided the kingdom and Acrisius locked his daughter in a tower after learning that she would bear a son who would cause his death. Zeus, naturally, fell in love with Danaë and she bore him a son, Perseus. Thinking the boy to be his brother's child, Acrisius locked mother and child in a wooden ark and put them to sea. The tiny boat drifted across the water to the island of Seriphos, the realm of Polydectes, where they were saved by his brother, Dictys, a fisherman. Polydectes fell in love with Danaë and Perseus grew to become a strong and athletic young man. The king told Danaë that he wanted her to become his wife. She refused and Perseus came to his mother's aid. Pretending to seek another princess' hand in marriage, Polydectes shamed Perseus into giving him as a wedding gift the head of the Medusa, believing this would be the end of Perseus' interference in his quest to make Danaë his wife

With the help of Athena, Mercury and Hermes, Perseus set out on his quest. Athena gave him a mirror-shield. He would be able to look at the reflection of the Gorgon without turning to stone. Mercury allowed Perseus the use of his winged sandals so he would be able to fly to the island where Medusa lived with her sisters, the helmet of Hades that would render him invisible and the kibisis, a bag into which he could place the head of the monster. Hermes crafted a magic sickle that would cut through the Gorgon's neck with one blow. Equipped for battle, Perseus flew to the land of the Hyperboreans where Medusa and her sisters lived. There surrounded by frightening statues of previous victims, Perseus put the helmet on his head, slipped past Medusa's sisters, and approached the sleeping Gorgon backwards, watching her reflection in Athena's shield. When he could hear her breath and the hissing of the serpents in her hair, Perseus cut off her head with one swipe and placed it in the kibisis. Pegasus and his brother Chrysaor, children of Poseidon's conceived during an ill-fated liaison, flew from the neck of the monster.

Flying back home by way of northern Africa, Perseus stopped near the Hesperides and visited with Atlas. Wishing to stay for a few days and asking the Titan for permission, Perseus was insulted when Atlas refused. Removing Medusa's head from the kibisis, Perseus changed the giant to stone known today as the Atlas Mountains.

Continuing across Africa, he flew over Philistia, where he encountered the sight of the beautiful Andromeda chained to a rock. A sacrifice to appease the Nereids, nymphs who served Poseidon. Andromeda's mother, Cassiopeia, was a beautiful woman who claimed her beauty was greater than that of the Nereids. To punish Cassiopeia, the sea god sent the monstrous Cetus to destroy Philistia, its ships, coasts and people. Cepheus the king and Cassiopeia went to the oracle to learn what needed to be done to stop the destruction. After being told that the sacrifice of their daughter would be the only protection against the horrific monster, the tearful parents chained Andromeda to a rock on the beach and awaited her fate. Perseus offered to kill Cetus on the condition that they give him Andromeda's hand in marriage. Meaning to turn the monster to stone with the head of the Gorgon, Perseus flew into the sky above Cetus. Instead, the sea monster attacked the man's shadow on the surface of the water. Perseus flew down and cut off its head with his sickle. Perseus married Andromeda and flew back to Seriphos with her.

Polydectes believed that Perseus was dead when he didn't return from his quest. The king decided he didn't need to pretend that he planned to marry another princess and set his mind to taking Danaë by force. She fled to the temple of Athena where Polydectes couldn't follow. The king had the temple surrounded and refused her food and water until she married him. Pulling the head of Medusa from his bag, Perseus turned Polydectes and his generals to stone. The king's brother Dictys, who had pulled the infant Perseus and Danaë from the sea, became a wise and benevolent king. Perseus, Andromeda and Danaë returned to their original home in Argolis where he became king when his grandfather Acrisius fled. Perseus reunited the two halves of his great grandfather's land. Some years later, at the funeral games of a neighboring king, Perseus threw a discus. It landed wide of its mark and fell into a crowd of spectators. The discus hit Acrisius, killing him and fulfilling his prophesied death at the hand of Danaë's son.

Egypt: a linkage of the legend of Proetus, Danaë, Perseus, Acrisius and the floating ark may occur with the story of Isis, Osiris, Set and the infant Horus. In this interpretation, Osiris (Proetus) is united with his sister-wife Isis (Danaë) producing their son Horus (Perseus). The jealous Set (Acrisius) kills his twin Osiris, cutting the body into many pieces and throwing them into the Nile. He was punished by Horus as revenge. The ark represents the boat of acacia wood used by Horus and Isis to search for the pieces of Osiris' body.

Christian mythology: the constellations of Perseus and Cetus became St. George and the Dragon and occasionally David and Goliath. Later still, Perseus represented the Apostle Paul with the head of the Gorgon described as being the Holy Bible.


? Persei, "Algenib(side) or Mirfak(elbow)" Is s super giant star. It has a spectral class ofF5 and an apparent magnitude of 1.9. It’s distance from earth is470 Light Years, which means that at 10 parsecs (the distance at which the absolute magnitude is based upon) it would be around -1.5 (as bright as sirius).

? Persei, "Algol” (demon), is an eclipsing variable. It has two components ranging in magnitude between 2.2 and 3.5. over a period of just under three days. Distance from Earth 82 Light years.

? Persei, is a giant with a spectral class of F7 – it has a surface temperature of around 7000 degree’s K. It has a magnitude of 3.1 and lies just over 200 hundred light years away. This gives an absolute magnitude of -0.9.

? Persei, is a star at a distance of 100 light years. It’s apparent magnitude is 2.96 and belongs to spectral group B1, a group of helium stars. At 10 parsecs it’s magnitude would be around -3.

? Persei, “Menkhib or Menkib” is another super giant of spectral class B1, this star has a surface temperature of around 20,000K. This star is around 820 light years away and has an apparent magnitude of 2.91. This gives an absolute magnitude of -5.3.


Deep Sky Object in Perseus.

NGC869 and 884, The double Cluster, the famous Double Cluster. These are a pair of bright open clusters that are a sight to behold in almost any telescope. Personally I would suggest the lowest power that you have - try for a little Sky around the cluster in the EP. Both Clusters are around 7000 Light Years away. These clusters are around 200 light years apart (from each other). The combined magnitude is 6.1 and is naked eye from a dark site. The double cluster is around the same size as the full moon, 30'.

M76(Little Dumbbell), Mag 12, 3.2'. The little dumbbell is popular amongst observers - it resembles it's larger and brighter namesake. A small telescope will reveal the hour glass shape. Averted vision will help in seeing the two distinct lobes and wisps... It was once thought that this object was in fact two objects (M76 still has two NGC numbers). M76 is one of the faintest messier objects.

M34(Spiral Cluster) Open Cluster, MAG 5.2, size 35 minutes.

NGC1499, California Nebula, Diffuse Nebula, Mag 5.0, 2,7 degrees

NGC774, Open Cluster, Mag7.9

NGC957, Open Cluster, Mag 7.6

NGC1220, Open Cluster, Mag 11.8

NGC1245, Open Cluster, Mag 8.4

NGC1444, Open Cluster, Mag 6.6

NGC1496, Open Cluster, Mag 9.6

NGC1058, Galaxy, Mag 11.9

NGC1528, Open Cluster, Mag 6.4

NGC1518, Open Cluster, Mag 8.4

NGC1545, Open Cluster, Mag 6.2

NGC1624, Open Cluster,Mag 11.8

NGC1342, Open Cluster, Mag 6.7

NGC1605, Open Cluster, Mag 10.7

NGC1342, Open Cluster, Mag 6.7

NGC1582, Open Cluster, Mag 7.0

NGC1499, California Nebula, Diffuse Nebula, Mag 5.0

IC1985 Diffuse Nebula, Mag7.3

I’ve only listed around 18 object’s for Perseus, but there are at least 60 within the constellation boundaries.


Double Stars in Perseus

Eta Perseus STF 307 AB (15 Per) RA: 2h50m41.80s DE:+55°53'44.0"

Magnitude: 3.76/ 8.50

Located in the Northern part of the constellation about 3 degrees south of the famous Double Cluster. This is an easily split pair with a beautiful contrast in colours the primary being Orange and the companion blue. The primary is a Super Giant Star of spectral class M3 and companion is spectral class A0. Despite the difference in magnitude 3 the separation of nearly 30” means even the smallest of scope should be able to split this pair. First observed in 1779 by William Herschel the companion is currently at position angle 301 degrees (WNW) of the primary. The Primary is around 1300 Light years away and both stars share a similar motion through space. At low powers the sounding field is rich in stars.

Epsilon Perseus STF 471 AB (45 Per) RA: 3h57m51.20s DE:+40°00'36.0"

Magnitude: 2.85/ 8.88

Located down the Eastern leg of Perseus this pair can be a tough split in a small telescope magnification of at least x100 will be required the primary is a variable of the Beta Cephei type and with a spectral class of B0.5 and appears blue/purple. The secondary is an A2 and appears white with a hint of blue. The separation is currently 9” and the primary can overwhelm the secondary. The Primary is located about 550 light years away this pair was first observed in 1780. The secondary is currently at a position angle of 9 degrees (N). This one to save for nights of good seeing.

Zeta Perseus STF 464 AB RA: (44 Per) 3h54m07.90s DE:+31°53'01.0"

Magnitude: 2.85/ 9.16

Another tough split for smaller scopes but this pair can be split when conditions are favourable. The larger scope should split with a x150 magnification smaller scopes may require x200. The Primary is a blue super giant that appears white or pale blue when observed. The secondary is too faint to show any colour but being a B class main sequence star would also appear blue/white. The pair is currently just less than 13” apart and the secondary is at 208 degrees (SSW). The Primary is around 1000 light years away and the field shows several stars of 9th/10th magnitude.

HD22503 STF 552 RA: 4h31m24.10s DE:+40°00'36.0"

Magnitude: 6.78/ 7.18

About 6 arc minutes too the east of Epsilon Perseus are a very evenly matched pair, both are class B8 main sequence stars and appear as two white diamonds set in a very rich field. They are easily separated at 9” with the secondary being at 116 degrees (ESE) and can be seen in the smallest of scopes with moderate power. This pair were noted in 1828 are believed to be around 1700 light years away. Although not this is not a colour contrast pair they still make a very fine sight.

HD18537 STF 331 RA: 3h00m52.10s DE:+52°21'06.0"

Magnitude: 5.21/ 6.17

Moving back towards Eta Perseus, draw a line between gamma and tau Perseus aim mid way and drop down about a degree and you will find an attractive pair of stars of 5th and 6th magnitude. The primary is usually seen as white and the secondary has a strong blue colour but both can appear white or blue. This pair is again made up of two B class stars the primary being B7 and the secondary B9. First observed in 1800 the calculated distance to the primary is 800 light years and to the secondary 700 but both stars share common proper motion through space. The separation of around 12” with the secondary at 85 degrees (E) makes this an easy pair to split.

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