Skywatch September 2001

 NOTE: Times given in the scripts are all local Schenectady, New York time.

Saturday, September 1st to Sunday, September 2nd. Written by John Schroer

Sky watchers of the Capital district will have a bright sky to observe during this last weekend of summer, with a planet and a full moon to view.

This brightening of the evening and night sky is due to Earth's closest neighbor, which is the Moon. It will reach Full Moon Phase on Sunday. Known to farmers as the Harvest Moon it takes a long path across the southern sky. This permits farmers to harvest their crops late into the night, working by the light of the Moon. Other names for the September Full Moon include the Chrysanthemum Moon by the Chinese, the Nut Moon by the Cherokee, the Mulberry Moon by the Choctaw, Singing Moon by the Celtic peoples, and the Barley Moon by the medieval English. On Friday the Moon will rise at 6:54 PM; while on Saturday the Moon will rise at 7:25 PM. The Moon will rise on Sunday at 7:51 PM.

Only one planet is visible to earthlings in the late summer sky. It can be spotted in the southwestern sky as a bright reddish light. Mars, the Red Planet, is now in the constellation of Sagittarius the Archer. Most sky watchers recognize this constellation as a teapot, with Mars just above the spout. Mars is located due south at 7:58 PM on Friday, reaching due south two minutes early on Saturday, and again on Sunday. It will set around midnight during the Labor Day weekend.

The zenith or top of the sky is filled with many bright stars as the Summer Milky Way rises higher with each passing night. Look for the brightest one with a suggestion of blue in its light. Named Vega, it is the brightest summer star and is found in Lyra the Lyre or Harp. It is 27 light years away, or approximately 162 trillion miles from Earth. The rest of the constellation Lyra appears as a parallelogram or slight tilted rectangular box made of fainter stars than Vega. The fall stars are now making their presence known as they rise in the eastern sky over the Capital District. Due east, and just above the eastern horizon is a box of four bright stars. Knows as the Great Square of Pegasus, they mark the body of the flying horse, friend to Perseus the hero.

The Albany Area Amateur Astronomers is an active group of hobbyists that explore the universe for the fun and excitement of exploration and sharing a common interest in the skies above. Anyone interested in exploring astronomy as a hobby should call Alan and Sue French at (518) 374-8460, or call the Schenectady Museum at (518) 382-7890 for further information

You can find more information on the night skies by staying in touch with the Dudley Observatory Skywatch line or by visiting the Dudley Observatory web site at http://www.dudleyobservatory.org. Skywatch Line is Open Daily after 5 PM Monday through Friday.

Monday, September 3rd. Written by Joseph Slomka.

Tuesday, September 4th. Written by Jonathan Cassidy.

The "Summer Triangle" is at its zenith this month. Over head each night you will find a large triangle of bright stars. Starting with Vega, in the constellation Lyra, directly overhead at sunset proceed east to the next bight star that pops out. This is Deneb in Cygnus. Next go south to Altair in Aquila.

These three stars mark the "Summer Triangle". This triangle wheels over us from June, when it is low in the east, till October. They are bright enough that they can be seen even from highly light polluted in city locations. Indeed they may be the only things in the sky you can see, so being able to identify them would make you look like a wizard to your friends.

This is the season of fewest number of bright stars, first magnitude. Only two other can be seen: Arcturus to the west and Antares to the south.

From a dark sky location you will see a portion of our home glx., the Milky Way, goes through the center of our triangle. There is even a dark lane visible blocking out a part of the Milky Way, with bright streams of stars on either side. This is a dust cloud in the Milky Way. It blocks our view of the core of our home glx.

Wednesday, September 5th. Written by Ray Bogucki.

As our tiny planet whirls through space, rotating on its axis and revolving around the Sun, it occasionally happens that the Earth lines up precisely with two other bodies in the solar system. Sometimes the alignment occurs between one other solar system object and a distant star. These events are known as occultations and are followed with great interest by both professional and amateur astronomers. Perhaps the most obvious and spectacular alignment occurs when the Moon passes directly between the Earth and the Sun, producing a total eclipse. Many people consider this event to be the most awesome celestial spectacle there is and simply allow themselves to be overwhelmed by the sight. More professional folks busy themselves with recording important information about the Sun's corona and prominences during the few minutes of totality.

When the Moon overtakes and occults a bright star, which is essentially a mathematical point of light, the star appears to reside for a few seconds on the limb of the Moon and then vanishes in an instant. A different effect is noted when the Moon occults a planet, which, while small, displays real dimensions in a telescope. Last month the Moon occulted Jupiter and it can take minutes for the edge of the Moon to creep across the disk of this gas giant. Unfortunately, this area was just a little too far north, and those observers who were not clouded out saw the Moon skim just below Jupiter. We get another chance this week as the Moon occults the ringed planet, Saturn, on Monday morning, September 10. The lucky folks in San Diego will watch the occultation begin at 4:50 a.m., in the dark sky just before morning twilight.

We have to settle for observing the event well after sunrise, beginning just after 9:20 a.m. Fortunately, Saturn's rings are tilted at a wide 26 degrees to our line of sight, greatly increasing the sunlit area and rendering the planet easily visible in a telescope or binoculars even in broad daylight. It should take well over a minute for the Moon to cover the planet's rings completely, from tip to tip. Then, just an hour later, Saturn will slowly reappear from behind the dark edge of the last quarter Moon. Because the faint earthlight on the dark half of the Moon will be completely washed out by the bright blue of the sky, the planet will seem to emerge "out of the blue" from nowhere.

Thursday, September 6th. Written by Peter Jennes.

The mythological characters Cepheus, Cassiopeia, Andromeda, and Perseus are linked together in legend and astronomy. For thousands of years, the story of the king, his queen, their daughter, and the hero who rescued her has played itself out each night as the constellations slowly spin around Polaris. Cepheus, the King and almost hapless bystander in these legends is commemorated in a constellation containing an asterism of stars that looks amazingly like a child's drawing of a house.

During September, the stars of Cepheus are high in the northeast around 10 PM. At that time, you can find the house of this legendary king with its roof slanted towards the horizon. To the right of Cepheus sits the familiar W of his queen, Cassiopeia and above the king, Cygnus the Swan points backward towards the basement of the house. The five principle stars forming this wide, 10 degree asterism are all near third magnitude and they are just visible from suburban areas.

  Although the stars of Cepheus are much dimmer than the brightest stars that light the night, this constellation holds many celestial wonders. The star marking the peak of the roof was known to the ancients as Er Rai, the Shepherd. Presumably, this name dates back to a time when this celestial region represented not a king, but a shepherd driving his flock of stars through the hills of the sky. Proceeding clockwise from Er Rai, the next star in the house asterism is called Alfirk or "the flock." Continuing clockwise, the next star is Alderamin, the brightest star in Cepheus. Eighteen thousand years ago, when civilization was just emerging from its Ice Age origin, Alderamin marked the North Celestial Pole.

  Cepheus holds two other stars of great interest to astronomers, Mu Cephei and Delta Cephei. Mu Cephei is a red supergiant that is also called the Garnet Star. The Garnet Star has a deep red color implying it has an extremely cool surface. In fact, measurements show this starís surface temperature is about three thousand degrees and water vapor has been detected in its spectrum. Delta Cephei is a yellow giant that varies between magnitude 3.6 and 4.3 over a five-day period. This star is the prototype Cepheid variable, a class of star used as a "standard candle" to gauge distances between local galaxies.

Friday, September 7th to Sunday, September 9th. Written by John Schroer

Monday, September 10th. Written by Joseph Slomka.

The Sun sets at 7:14, with night falling at 8:52 PM. Dawn begins at 4:55 AM. and ends with sunrise at 6:31.

As the sky darkens, the planet Mars blazes due South. Binocular observers are in for a treat. Mars points to several worthy objects. Mars is in the midst of the Milky Way, that glorious band of stars that stretch from North to South. Just scanning the Milky Way is rewarding. But a few objects deserve special attention. Two and a half degrees North of Mars lies the Lagoon Nebula. Another degree and a half north lies the Triffid Nebula. Both are glowing clouds of gas, divided by deep rifts of cosmic dust. Both are star forming regions, wherein stars illuminate their cocoons of gas and dust. Five degrees East of Mars is M 28, a densely packed star cluster. All these objects are within one binocular field of Mars.

Dawn skies include similar bounty. The beautiful Pleiades are a great binocular object high in the eastern sky. Creamy white Saturn lies below; binoculars cannot see Saturn's rings, but at least shows the oblong shape that betrays their presence. The Last Quarter Moon is next lowest; scanning the Moon with binoculars is always a rewarding experience. Jupiter is next; binoculars easily show the four moons, first discovered by Galileo. Venus is found above the treeline. It is the brightest in the lineup.

Capricornus, up by twilight's end, is a strange constellation. It begins a series of constellations that have some relation to water: Aquarius, Pisces, Cetus, Eridanus, and Pisces Austrinus. Capricornus is normally called the "Sea Goat." Obviously no such animal exists. The name "goat-fish" is of Sumerian origin; it represents the Babylonian god Ea , the god of the subterranean fresh water ocean. The geographic term "Tropic of Capricornus" denotes the southern latitude in which seasons begin, winter when the northern hemisphere has summer. In ancient times, that occurred when the Sun occupied Capricornus; now, several thousand years later, that event occurs in the constellation Sagittarius.

Tuesday, September 11th. Written by Jonathan Cassidy.

In the constellation Lyra, marked by the brightest star of the night Vega, we have an example of the type of death our own sun will endure some time in the future.

Looking directly over head at the end of twilight find the brightest star, this is Vega. Once twilight has faded look south of Vega to find a nearby parallelogram of dimmer but equal brightness stars. Looking between the south most pair of stars in this parallelogram there is a planetary nebula.

Planetary nebulae look like rings or clouds of gas orbiting a central place. Usually there is a star there but we can not always see it. This nebula in Lyra is called the "Ring Neb." Because it looks like a ring of gas. It is actually the blown out outer shell of a star that is now a white dwarf.

Theory has it that the star had been similar to our own sun. It is expected that our sun will go through a similar phase in 3 - 5 billion years, you can wait around if you want to, I have shopping to do.

The Ring nebula is also called M 57 as it is the 57th item discovered by M. Messier and his team of comet hunters who observed in Paris in the mid 19th century. The Ring Neb. can be seen with a small telescope with good optics. It will look like a dim round fuzzy patch larger and dimmer than surrounding stars.

Wednesday, September 12th. Written by Ray Bogucki.

At nightfall, Mars continues to shine low in the south, diminishing in both size and brightness during this month as the Earth pulls away. It is currently moving eastward through the constellation, Sagittarius, the Archer. This is a constellation of bright stars, including the well-known "Teapot" asterism. During this week, Mars will pass close to the top star in the lid of the "Teapot". Sagittarius contains 15 Messier objects which include globular clusters, open star clusters and nebulas. In addition it is placed in the densest and brightest section of the Milky Way which marks the hub of our galaxy. At the winter solstice, the Sun lies in Sagittarius close to M8, the famous Lagoon Nebula.

The constellation of the Zodiac that follows Sagittarius is Capricornus, the mythical Sea-Goat. Capricornus, while large in area, presents a stark contrast to its bright neighbor. It has only relatively faint stars, lies outside the Milky Way and contains only one Messier object, M30, a globular cluster. Yet Capricornus holds some important historical and geographical interest.

When the outermost giant planet, Neptune, was discovered in 1846, it was found in Capricornus, very close to the position predicted by the French astronomer, Le Verrier. With its orbital period of 165 years, Neptune will not return to the same location where it was discovered until the year 2011, but it has now returned to Capricornus and can be found near the western boundary of the constellation, about 14 degrees west of Uranus, which is also in Capricornus. It was irregularities in the motions of Uranus that led Le Verrier to calculate the orbit of the then unknown planet beyond the orbit of Uranus.

In the area of geography, the Tropic of Capricorn, the line of latitude 23 and a half degrees south of the equator, was named for Capricornus. It is the southernmost latitude where the Sun reaches the zenith at noon on the December solstice. When the ancient Greek astronomers were plotting the motion of the Sun in our sky, its southernmost position or solstice occurred when the Sun was in Capricornus. 2000 years of precession have moved the solstice into Sagittarius. In the year 4000, it will lie in Scorpius.

Thursday, September 13th. Written by Peter Jennes.

  Sunset for tonight, Thursday, September 13th will be at 7:10. The moon is now about three days away from new and does not rise until nearly 3 AM. As it the sky gets dark, the Great Square of Pegasus sits half way to the zenith in the east. Around the Square, the two celestial fish swim through the zodiacal sea. These two zodiacal fish are Pisces and Pisces Australis. Pisces swims on the left side of and below the Great Square of Pegasus and to the right sits Pisces Australis, the lesser-known southern fish. The Great Square asterism belongs to the traditional autumnal constellation Pegasus. By 1 AM, more autumn stars including the Pleiades and Taurus will all be above the eastern horizon along with Jupiter and Saturn.

Even as the stars of autumn begin to appear in the late evening sky, the stars of summer stubbornly hang on in the evening sky. As testimony to the tenacity of summer, One last bright star of summer reaches its peak altitude above the southern horizon over the next few weeks. This bright star is Fomalhaut, the southernmost bright visible from our area. Right now, Fomalhaut rises around 10:30 and reaches its greatest elevation about 1:30. However, even at its greatest elevation, this star is only about 15° above the horizon.

Fomalhaut is the only bright star in the southeastern sky after 10:30. If you aren't sure that you are looking at the right star, you can also use the two stars on the right (or western) side of the Great Square of Pegasus. A line through these two stars will point due south towards Fomalhaut. The most common translation for the word, "Fomalhaut" is, "mouth of the fish." The fish in this case is the "Pisces Australis." the southern fish. This constellation is different from the zodiacal constellation Pisces. The zodiacal Pisces does not contain any prominent stars.

Although these constellations are separated in space, they are not separate in legend. In some early legends, the Southern Fish was said to be the father of the zodiacal Pisces. However in Greek sky lore, the Southern Fish came about when the Greek deity, Venus transformed herself into a fish to escape the monster Typhon. Now, many people see this fish as drinking the water spilling out of the water jar carried by the constellation Aquarius.

Friday, September 14th to Sunday, September 16th. Written by John Schroer

Sky watchers of the Capital district have a more interesting sky to observe during this last weekend of summer, with two planets and late crescent moon to view.

This darkening of the evening and night sky is due to Earth's closest neighbor, which is the Moon. It reaches an age of 26 and one half days tonight, meaning that the Moon is a very small, shrinking crescent, setting before the sun sets. In fact, the Moon will not be easily seen, due to its closeness to the Sun. The Sun sets at 7:05 PM on Friday, while setting two minutes earlier tomorrow on Saturday, and at 7:02 on Sunday. This permits more people to stargaze, due to the darkness of night arriving earlier each day.

The first of our two planets now visible in the skies over the Capital District includes a bright reddish light in the southwest.. Mars, the Red Planet, is now in the constellation of Sagittarius the Archer. Most sky watchers recognize this constellation as a teapot, with Mars just above the spout. Mars sets at 11:47 PM tonight, 11:45 PM on Saturday, and 11:44 PM on Sunday

The other planet now visible is seen in the eastern sky later in the evening. Look for Saturn, the Ringed Wonder, as a bright yellow light around 11 to 11:30 PM, depending on how low your eastern horizon is at your location.

Rising shortly before Saturn the skywatcher may spot a small cluster of stars looking like a miniature dipper. These stars are the Pleiades, a bright open cluster of stars riding on the shoulders of the constellation Taurus the Bull. The Pleiades, also known as the seven sisters, rise into the sky in the east around 9:30 PM during this weekend. The appearance of the Pleiades announces the arrival of autumn in the coming week.

The Albany Area Amateur Astronomers is an active group of hobbyists that explore the universe for the fun and excitement of exploration and sharing a common interest in the skies above. Our next meeting is Tuesday, September 18th at 7:30 PM in the Schenectady Museum. All are welcome!

You can find more information on the night skies by staying in touch with the Dudley Observatory Skywatch line or by visiting the Dudley Observatory web site at http://www.dudleyobservatory.org. Skywatch Line is Open Daily after 5 PM Monday through Friday.

Monday, September 17th. Written by Joseph Slomka.

Tuesday, September 18th. Written by Jonathan Cassidy.

The Dolphin is at its best these nights. One of the smallest constellations is Delphinus, the dolphin. It has no bright stars and its main figure is made up of just 5 stars that are medium bright.

You can find it from anywhere but the most light polluted areas by looking straight over head at the end of twilight and finding the one brightest star, this is Vega.

From Vega go south east to the next brightest star, this is Altair in Aquila the Eagle.

From Altair go east about one fist width to a group of five stars, four of which make a small diamond. This diamond is the head of the dolphin with the fifth forming a "tail". Note that all the five are of similar brightness. This is one of the few constellations that is easy to see the figure that it represents.

Here is the interesting part; two of the stars have names: Sualohcin and Rotanev. These names appeared in a catalogue of star compiled in 1814 by the Palermo Observatory. The names were a mystery till it was noticed that in reverse they spell Nicholaus Venator, an astronomer at the observatory.

Wednesday, September 19th. Written by Ray Bogucki.

All five bright planets are currently visible in the sky, and the three rocky inner planets are having close encounters with bright stars. Mercury now stands at its greatest eastern elongation from the Sun, and shines less than one degree below the first magnitude blue-white star Spica, in the constellation Virgo. Look for this sparkling pair a half-hour after sunset, low in the west, lying about 10 degrees below and a little to the right of the young crescent Moon. Binoculars will help to find them in the bright twilight. When the sky darkens, Mars can be found low in the south, still shining at brighter than zero magnitude, and lying just below third magnitude Kaus Borealis, the star at the top of the lid in the "Teapot" in Sagittarius.

In the early morning sky, brilliant Venus has been bearing down on first magnitude Regulus, in the constellation Leo. For the next two mornings look for this close pair low in the east about an hour before sunrise. Extending upward from Venus are the two gas giants Jupiter and Saturn in that order. The line formed by the three planets nicely delineates the plane of the ecliptic. Jupiter is in the constellation Gemini and lies a little to the southwest of the twin stars, Castor and Pollux. Saturn is found a few degrees east of Aldebaran, the red eye of Taurus, the Bull. Saturn is close to quadrature, the orientation in which the Sun casts its light somewhat from the side as viewed from Earth. The shadow of the planet's disk cast on the rings behind give Saturn a wonderful 3-dimensional appearance in a telescope.

The coming week will have moonless mornings, providing us the opportunity to glimpse the phenomenon known as Zodiacal light. From a dark sky location, search the eastern sky about 4:30 a.m., well before morning twilight, for a ghostly triangle of white light rising along the ecliptic in the same line as the planets. This faint light, about as bright as the Milky Way, is assumed to be sunlight reflecting from the countless tiny particles that fill the ecliptic plane in the inner solar system. These particles are believed to result from collisions among asteroids in the asteroid belt and are orbiting the Sun as they slowly spiral in, eventually to be captured by the Sun.

Thursday, September 20th. Written by Peter Jennes.

With the head of a goat and the tail of a fish, Capricorn is one of the most bizarre creatures in the celestial zoo. Although Capricorn is a zodiacal constellation, its brightest stars are all between third and fourth magnitude which can make the constellation a little difficult to find. This mythological sea goat occupies the region of space to the left of Sagitarius and below Altair. From a reasonably dark location, Capricorn's outline looks like a broad triangle with a slightly crushed in top and bent sides. The head of the sea goat is a star named Al Gedi. This fourth magnitude star occupies the upper right corner of the triangle and lies nearest to Altair. Al Gedi is a wide, optical double star. The two stars appear to be separated by 376 arc seconds but this is only an illusion. In reality, these two stars are separated by hundreds of light-years and only a chance alignment makes them look like a double star. Since both of these stars are fourth magnitude and widely separated, you should be able see both stars without using binoculars.  

About three degrees below Al Gedi lies the third magnitude star Dabih. Dabih is also a double star but unlike Al Gedi, Dabih is a true double star. Dabih's two components are separated by less than four arc-minutes. The brightest member of the pair is a dazzling white third magnitude star while the other member is a sixth magnitude blue star. Because they are relatively close and quite different in brightness, you will need a telescope to observe the pair. If seeing seeing is steady, you may also see a ninth magnitude star making a neat equilateral triangle with the brighter two stars.

Friday, September 21st to Sunday, September 23rd. Written by John Schroer

This weekend brings the start of a new season, a crescent Moon, and some new planets to view for Capital District skywatchers.

First, the Moon returns to the evening sky. Now seen as a thin crescent, it will grow larger with the passing of each day, and set a little later each night. Many early cultures used the Moon as the basis of their calendar. Indeed, the Jewish and Islamic faiths still use the Moon for their calendars to this day. In addition, the Christian faith sets the First Sunday after the First Full moon after the Vernal or Spring Equinox as Easter Sunday. Skywatchers with telescopes can observe the lunar dawn breaking across the rugged mountains and craters of our nearest neighbor, if they watch the Moon each evening.

On Friday, September 21st at dusk, you can see an orange star to the lower left of the Moon. This is the bright star Antares, known as the Heart of the summer constellation, Scorpius the Scorpion. Much higher and to the far left, look for a brighter orange light which is the Planet Mars. Mars is located in the constellation of Sagittarius. Many skywatchers see the bright stars here forming a picture of a teapot.

SATURDAY is a special day, for it brings the season of Autumn to the Capital District. Arriving at 7:04 PM, the Autumnal or Fall Equinox marks the exact time that the Sun crosses the equator, as it moves south for the year, marking the start of fall in the Northern Hemisphere and spring in the Southern Hemisphere. Antares now shines to the lower right of the Moon, as the Moon continues in its orbit.

Saturn and Jupiter are now on the move, appearing in the eastern sky late at night. Saturn rises around 10:45 PM, in the constellation of Taurus the Bull. Saturn is the brightest of the lights in the eastern sky. Just look for its telltale yellowish color. Jupiter is for night owls, rising around 1 AM. Jupiter, due to its size and it being located half the distance that Saturn is, will be appreciably brighter.

Thank you for calling Dudley Observatoryís Skywatch Line. For more information on Dudleyís programs and activities, log onto Dudleyís website. http://www.dudleyobservatory.org

Monday, September 24th. Written by Joseph Slomka.

The Sun sets tonight at 6:49, and ends with nightfall at 8:24 PM. Dawn begins at 5:11 AM tomorrow, and ends with sunrise at 6:46.

After sunset, the First Quarter Moon becomes obvious due South. It also lies about two degrees above Mars, the bright red planet in the Teapot's dome. Because of the Moon's brilliance, faint objects like nebulae and the distant planets Uranus and Neptune are not readily seen. Mars is noticeably smaller, but still a worthy telescopic object.

Pre-dawn skies are more interesting, Saturn lies high in the South, in the middle of the constellation Taurus. Jupiter is midway between Saturn and the horizon. Jupiter's four moons are easily seen in binoculars, and always fascinating. Venus is the brightest, but also the lowest, near the horizon.

If you look straight up at the Northern Sky, you will see Cepheus, a constellation shaped like home plate. One of its stars, Delta, proves very interesting. This star varies in brightness precisely once every five days, eight and three-quarters hours. However, these stars do not vary very much in brightness. They are generally supergiant stars about 25 times the Sun's size. Such stars, called cepheids, are very important for they are "measuring sticks of the universe." Astronomers have discovered that the longer the period, the more luminous a star is. Luminosity means the actual brightness of a star. Thus, if we know how luminous a star really is, and how bright it appears in our telescopes, we estimate how far away the star is. Seven hundred such cepheids have been discovered, and now astronomers have a good idea how far away such objects as the Andromeda Galaxy really are. Why do these stars pulsate? No one knows. Some think that it is a battle between the nuclear fires trying to expand, and gravity trying to hold the fires in. But such theories do not explain the precise timing of these changes. Consult a star chart and follow Delta Cephei changes for a week and see for yourself.

Tuesday, September 25th. Written by Jonathan Cassidy.

A galaxy to watch for. Just coming up now in the eastern sky at night is the galaxy Andromeda. From any dark sky location you can see this with your naked eyes. From most suburban locations you can get a very fine view with binoculars.

To find the Andromeda galaxy go to the "W" in the eastern sky that represents the constellation Cassiopeia. From the south most "V" of the "W" follow the point of the "V" in a line east toward the next brightest star. Two thirds of the way along this line, before you get to even a dim star, is a brightened patch. This patch can not be called a point it is definitely a smudge in the sky it is the Andromeda galaxy. You may need averted vision to find it. Try to look at it with your center of vision to the upper right of the actual place.

The Andromeda galaxy is one of the heavy weights of our local group. It is over 2 million light years away and is the most distant object the average person can see naked eye. From a dark sky place some people have seen M 33 the Pinwheel glx., but it is too dim for the average eyes to see.

Thus in a night one can see our nearest neighbor, the Moon, and our nearest galactic neighbor and most distant naked eye site the Andromeda Glx. There are other ways to find the Andromeda Glx. we cover those in future sky watch line reports.

Wednesday, September 26th. Written by Ray Bogucki.

When Galileo first turned his telescope to the night skies in 1609, one of the first objects he studied was the planet Jupiter. He was fascinated by the four points of light that hovered near the planet in different arrangements but always in a nearly straight line. He quickly came to understand that these four points of light were moons revolving around Jupiter at different distances and with different periods, which he measured accurately. He also observed that when the moons were approaching or emerging from the area behind the planet, they would often disappear for a short period. With his usual keen insight, he concluded they were being eclipsed as they plunged into the invisible shadow of their giant parent. Galileo's calculations allowed him to predict such events with great accuracy, thereby lending major support to Copernicus' theory that the Earth and all the planets revolve around the Sun.

Today, almost 400 years later, Jupiter remains an object of endless fascination for amateur astronomers. The planet looms so large and its moons so bright that the clockwork movement of the four Galilean satellites can be followed easily with a small telescope or even with good binoculars. Jupiter is now well-placed for observing from northern latitudes since it stands at a declination of 22 degrees north, about as far north of the celestial equator as it can reach.

Tonight Jupiter rises in the east at about midnight, and at 2:37 a.m., in a classic Galilean event, its outermost moon, Callisto, approaching from the west, will disappear into the planet's shadow to reappear about 50 minutes later. Then, Friday morning in early twilight, about 6 a.m., all four satellites will lie on one side of Jupiter as Callisto joins the two innermost moons, Io and Europa, to form a tight group of three, east of the planet, while Ganymede lies a bit farther out.

In October, Io and Europa will fall into sync and pass in front of Jupiter close together so that the shadows of both moons will be visible on the planet's surface at the same time. Times and dates of these double shadow transits will be noted in later Skywatch lines.

Thursday, September 27th. Written by Peter Jennes.

At sunset, a ten day old Moon hangs twenty degrees up in the southeast. As the Moon rises higher, the terminator will be near some of the most spectacular features on the Moon. Starting in the north, one of the most prominent features is the Jura Mountains which form the semi-circular shore of the Bay of Rainbows. The relationship between the Jura Mountains and the Bay of Rainbows is no accident. Billions of years ago, a giant impact created Bay of Rainbows and the mountains that outline the bay are actually the crater ramparts that were uplifted during that impact. After the impact, lava welled up onto the lunar surface and created the smooth surface of the bay.

The Jura Mountains bordering the Bay of Rainbows seem to rise almost vertically from this lava plain. The distinct rainbow shaped arc of these mountains, which gives the bay its name, is all that is left of the originally circular impact crater. As you follow the curve of the mountains from the northernmost point to the south, you will start and end at mountain peaks. The northernmost peak is called Laplace Promontory and the southernmost peak is the Cape of Heraclides. In between these two points, the Jura Mountains rise-up almost 10,000 feet. For a few hours at lunar sunrise, the steep slopes of the Jura Mountains shine like jewels as they catch the first glints of sunlight.

  Moving far south into the Moon's Southern Highlands, the terrain becomes a jumble of craters. Out of this broken landscape, two craters lie near the terminator and deserve special attention. Tycho and Clavius are about as different as two craters can be and therefore make an interesting comparison. Of the two craters, Tycho is smaller and has a prominent central peak. Tycho is nearly 53 miles in diameter and almost 3 miles deep. When lighting conditions are right, the craterís central peak cast dramatic shadows onto the terraces inside the crater. In contrast, Clavius is an immense crater nearly 140 miles in diameter. Craters of this size are called walled plains and as typical for these ancient structures, the floor of Clavius is peppered with more recent craters. The largest of these craters, Porter and Rutherfurd are both almost 35 miles in diameter and are impressive in their own right.

Friday, September 28th to Sunday, September 30th. Written by John Schroer

This weekend brings the ever brighter Moon, exploding stars and some new planets to view for Capital District skywatchers.

The Moon dominates the evening sky. Growing in apparent size as it orbits the earth, the moon is 11 and one half days old. Eighty seven percent of the earth-facing side of our nearest neighbor is now lit by sunlight. By Sunday evening, the Moon will be nearly full, which is said to be at an age of 14 and one half days. This marks the halfway point in the Moon's orbit around the earth.

On Friday, September 28th at dusk, you can see a ginger-ale-colored star low in the western sky. This is the bright star Arcturus, located in the constellation of Bootes ( BO OH TEES) the watcher or guardian of the Great and Little Bears. Much higher and at the top of the western sky, look for a brighter blue light which is the star Vega, the brightest star in the constellation of Lyra the Lyre or Harp. Slightly brighter than either of them is the fiery orange planet Mars in the south.

Saturday's sky features one of the best known star pictures or asterism. An asterism is a picture made up of stars, which is not officially designated as a constellation. Look low in the North by Northwest sky for three stars in a bent handle, and four stars in a cup, close to the horizon. This is the Big Dipper, located inside of Ursa Major the Great Bear. For once it's positioned nearly level, "holding water."

Saturn and Jupiter are now on the move, appearing in the eastern sky late at night. Saturn rises around 10:15 PM, in the constellation of Taurus the Bull. Saturn is the brightest of the lights in the eastern sky. Just look for its telltale yellowish color. Jupiter is for night owls, rising around 1 AM. Jupiter, due to its size and it being located half the distance that Saturn is, will be appreciably brighter.

Thank you for calling Dudley Observatory's Skywatch Line. For more information on Dudley's programs and activities, log onto Dudley's website. http://www.dudleyobservatory.org

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Dudley Observatory
107 Nott Terrace, Suite 201
Schenectady, NY 12308
(518) 382-7583
info@dudleyobservatory.org