Observing

  • 01-08-2015

    Stargazing in August 2015

    The August Night Sky

    The General Weather patterns

    August has a similar range of weather as July, and it often follows on from that of the previous month. Temperatures usually lose the elevations of July however, but northern winds may bring cool, dry and clear nights! Westerly winds combined with a depression usually bring in dull wet weather, whilst warm anticyclones usually result in heavy thunderstorms.

    From Earth

    Astronomical twilight still lasts for some time, but we will soon be able to observe in the late evening rather than the early morning.

    The Sun

    The Sun begins the month in Cancer and enters Leo in the second week of the month. You may like to notify other society members if you observe sunspot activity and don’t forget to use approved methods to observe the Sun.

    The Moon

    The Last Quarter is on 7th at about 02:05 in the constellation of Aries.

    The New Moon is on 14th at about 14:55 in the constellation of Cancer.

    The First Quarter is on 22nd at about 19:30 in the constellation of Libra.

    The Full Moon is on 29th at about 18:35 in the constellation of Aquarius.

    The Moon is at perigee (nearest Earth) on the 2nd and again on the 30th and at apogee (most distant from Earth) on the 18th.

    The Planets

    Mercury -- is not well placed for observation this month. On the evenings of the 6th and 7th Mercury follows Jupiter down in the evening twilight.

    Venus -- is at inferior conjunction on the 15th and is best seen late in the month. By the 31st it can be found, rising in the east in the constellation of Cancer, about 1hr and 35 mins before the Sun.

    Mars -- is progressing westward from the Sun after the conjunction in June and is best observed at the end of the month in the morning twilight. It is still not a significant object this month. It rises about half an hour before Venus, but is on the other side of the Sun.

    Jupiter -- is at conjunction on the 27th and is best found very early in the month, but it is not an object for serious observation. On the evenings of the 6th and 7th Jupiter precedes Mercury down in the evening twilight.

    Saturn -- can be found low in the sky in the south-west by the end of the month. For casual observers, Saturn will be most conveniently placed at the beginning of the month. Dedicated observers will be pleased with the open ring system, but with the planet over the other side of the Sun it is passed its best. A first quarter Moon on the evening of the 22nd will provide a photo-opportunity.

    Uranus -- rises around 21:30 at the end of the month and is becoming better placed to observe. It can be found in the constellation of Pisces at RA 1h 15m 1s, Declination 7º 12' 58"; in the south-east, at a magnitude of 5.75.

    Neptune -- rises an hour or so before Uranus and is slightly better placed for dedicated observers. At the end of the month at around 01:15, it can be found culminating in the constellation of Aquarius at RA 22h 41m 36s, Declination -9º 09' 11"; in the south-east. It has a magnitude of 7.83.

    Meteors

    The Delta Aquarids can be seen from about 15th July to 15th August, but are not noted for their brightness. There are two radiants to this shower. The southern stream, radiating from near the star Skat in Aquarius, has a maximum around about 29th July. The ZHR is about 20 with a medium atmospheric entry velocity.


    The Perseids can usually best be seen between 9th and 14th August, peaking with a ZHR of about 80 before twilight of the 13th this year. The new Moon is on the 14th allowing for dark skies all the way up until peak viewing of the shower just before dawn. The Perseid meteor shower is one of the most consistent performers, the meteors they produce are among the brightest of all meteor showers, some with persistent trails. The radiant is in the north of Persius. The Perseids are associated with Comet P/Swift-Tuttle.

    Lyra

    This constellation is not one of the brightest, but can be easily found by searching out α Lyrae, that is Vega, the brightest of the three stars that comprise the 'summer triangle'. Fourteen thousand years ago Vega was the pole star but lost its pre-eminent position due to precession. It will of course become the pole star again. The brilliance of Vega is partly due to its close proximity to us, only 27 light years, it was this brilliance that made it an obvious choice as the first star to be photographed (in 1850 at the Harvard Observatory, using the early daguerreo type process). Also, it was only the third star to have its parallax measured, in 1840 at the Russian National Observatory.

    β Lyrae, as Sheliak is also known, is a variable star of the R Lyrae type with a period of about 46 days. In fact Sheliak was the first discovered. There are a number of stars around it that can be used to compare luminosity and help you follow its cycle. M57 the Ring Nebula lies about 45 minutes of arc to the east of Sheliak. It lies at a distance of over 45,000 light-years.

    Greek Myths

    To the north east of Hercules is a small but beautifully formed constellation, Lyra, the Harp. Its origins can be found in the story of Orpheus and his half-brother Linus; both of whom were accomplished musicians. Their parents were Apollo the sun god, who was also the patron of music and poetry and his mother the muse Calliope.

    Both Linus and Orpheus came to noteworthy ends. Linus was killed by the young Hercules who struck him fatally with a lute, in frustration at his inability to master the instrument during a music lesson. Orpheus's death was more tragic.

    Orpheus was taught to play the lyre, or harp, so beautifully by his father that his songs charmed the wild beasts and even affected the plants and trees. It also charmed, and won the hand in marriage of the beautiful nymph Eurydice. Their marriage feast was attended by Hymen, a divine personification of the celebrations, but ominously the torch he bore was smoking, a very bad omen. Shortly after the wedding Eurydice was walking in her garden when Aristaeus, a shepherd who had become smitten with her, surprised her and she stepped backward onto a snake, which fatally bit her. She was transported to the underworld, and grieving for the loss of his young bride, Orpheus sang his heart out to express his distress. All who heard him were touched but none had the power to reverse Deaths decree. Such was his anguish that Orpheus resolved to journey to the underworld and win back the life of his love.

    He presented himself before Hades the ruler of the underworld and his wife Persephone, and sang of his grief at his loss. Even the ghosts of earthly wrongdoers paused in their torment to listen to his wondrous voice. So impressed were they that they agreed that Eurydice should return with Orpheus. Their only condition was that Orpheus should lead his bride, but not look back upon her until they both reached the mortal world.

    Orpheus joyfully agreed to this and set off with his bride. However, her footsteps were so quiet that Orpheus began to doubt her presence. They had almost reached the borders of the land of the living, when Orpheus could contain his anguish no more and he turned to see if she was still there. Immediately she vanished into thin air, returning once more to the stygian depths. Orpheus could not return to the underworld again and spent seven months grieving in a desert cave. His despairing songs attracted the attentions of a group of Thracian maidens revelling in wine and dance. He was abhorred by their gaiety and when he spurned their advances they stoned him to death and tore him limb from limb. His lyre they threw into the river Hebrus where it continued to play ghostly tunes as the waters flowed through its strings.

    Jupiter was so moved by the haunting melodies that even death could not still, and he placed the Lyre between Hercules and Cygnus the Swan as a small but distinctive sign, highlighted by the brilliant star Vega.


    David J Thomas

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