The Dudley Observatory

The second half of the calendar year is better than the first half for meteor watchers, and August is the best month of all. There are several meteor showers in August, but the best known and most widely watched are the Perseids. This meteor shower peaks each year around August 11-12. It is generated when the orbital motion of the Earth carries it through the cometary debris left by the comet, 109P/Swift-Tuttle. This large comet travels in a highly elliptical orbit, coming into the inner Solar System to swing around the Sun just inside Earth's orbit once every 130 years. Swift-Tuttle's passage has been recorded for at least its last 5 apparitions, dating back to the 14th century. Its most recent passage was in 1992. After each passage around the Sun, the comet recedes into the far reaches of the Solar System, almost out to the orbit of the distant planet Neptune.
At each inner passage, the heat of the Sun causes ice on the surface of the comet to vaporize, releasing many tons per minute of small particles of solid, ash-like matter. These particles continue in roughly the same orbit around the Sun as the parent comet. Over long periods these particles spread throughout the entire orbit so that each year on a given date, the Earth plows through this stream of particles. Moving at 40 miles per second, the particles collide with atoms and molecules of air in the upper atmosphere causing the particles to reach incandescent heat. Each speeding, white-hot particle ionizes a column of air as it passes through, causing the atoms and molecules to glow, much as neon atoms glow in a neon sign. This moving column of glowing gas, usually about 100 miles up, is what our eyes see as a meteor streak.
The peak of this year's display should come next Wednesday night into Thursday morning. The meteors appear brighter and more numerous after midnight, when the leading edge of the atmosphere collides head-on with the particles. Perseid meteors can be seen for several days before and after the peak, so check any clear night during the next week. The waning crescent Moon should prove to be only a minor nuisance after midnight.

The next few mornings present observers with a last opportunity to glimpse the planet Mercury, around 6 a.m., an hour before sunrise. Brilliant Venus is unmistakable, well up in the southeast, while Mars shines at first magnitude 20 degrees to the right and above Venus; Mercury at zero magnitude is near the horizon, 20 degrees below and to the left of Venus in a rough line with Mars. Mercury is now dropping back toward the Sun. In a few week it will pass behind the Sun at superior conjunction.

In the evening sky, the constellation Gemini, the Twins, is high up in the eastern sky between the planets Jupiter and Saturn. From its position between two planets, one can calculate that Gemini lies on the ecliptic, the imaginary circle in the sky travelled by the Sun as the Earth makes its annual orbit around the Sun. All of the planets and the Moon travel in a narrow band on either side of the ecliptic, because the planes of all planetary orbits are close to the plane of Earth's orbit. The constellations that lie along this path are known as the twelve constellations of the Zodiac. Gemini holds a special place in this group because at the summer solstice, on June 21, when the Sun has reached the northernmost point in its travel, and we experience our longest day, the Sun will be in Gemini, near the toe of the Twin, Castor.

Gemini is home to many interesting sights. It contains one Messier object, the elegant open star cluster M35, which is visible to the naked eye in a dark sky, as a cloudy patch close to Castor's toe. Because it is near the ecliptic, M35 is occasionally occulted by the Moon. This presents a fascinating sight to telescope viewers who can watch the edge of the Moon block out dozens of stars in succession as it drifts across the cluster. Gemini also harbors several bright variable stars and the famous "Eskimo" nebula, a planetary nebula which, in photographs from large telescopes, looks remarkably like the face of a person surrounded by the furry hood of a parka.

Historically, two outer planets of the solar system were discovered while they were in Gemini. In 1781, William Herschel first recognized that the faint bluish object then located near the midsection of Pollux was not a star, but a new planet, later named Uranus. 150 years later, Clyde Tombaugh, after a year of searching at the Lowell Observatory, found Pluto passing through Gemini.

Tonight should be the first good night for observing the Perseid meteor shower. The Perseids were one of the most exciting meteor showers during the 1990s, with outbursts of over seven meteors per minute. These outbursts were associated with particles shed by Comet Swift-Tuttle, which swung through the inner Solar System in 1992. With the comet now receding, the outbursts seem to have ceased, but the Perseids remain an active shower. The peak is likely to occur during the night of August 11/12 with a single observer rate of about 60 meteors per hour. Tonight the rate should be somewhere around 20 meteors per hour, and tomorrow night should be around 30 meteors per hour. Best observing is after local midnight (which is 1 AM because we're on Daylight Savings time) but some Perseids can be seen as soon as it becomes completely dark.

This shower is known as the Perseid shower because its meteors seem to radiate from the constellation Perseus. Perseids may be seen in any part of the sky, but their trails all point backward toward the parent constellation. Evening Perseids slightly favor the northeastern half of the sky. You usually see about one meteor every few minutes, although they often occur in bursts and lulls.

The typical Perseid is about as bright as the stars of the Big Dipper, but there are many both fainter and brighter. Some greatly exceed the brilliance of any of the planets or nighttime stars. Many are yellow; but blue, white, orange, and green are also common. Perseids often leave lingering trails, and occasionally one breaks up into colored pieces like a Roman candle.

To view Perseids, find a nice, dark place away from outside lighting; make yourself comfortable on a blanket or sleeping bag; point your feet northward; and look straight up. Perseids may appear almost anywhere in the sky, but the sky is usually clearest straight overhead.

Skywatch Line for Tuesday, August 10th, 2004, by Steven Russo, Planetarium Manager of the Suits-Bueche Planetarium at the Schenectady Museum

The sun will set tonight in the west northwest at 8:05. It will rise in the east northeast on Wednesday at 5:59 and set in the west northwest at8:03. The Moon is currently in a Waning Crescent phase, and will rise after midnight tonight, and will set at around 5:00 this evening.

Planet viewing is now at a minimum. Very, very low in the west you can locate the planet Mercury. But after darkness, it is too low to be seen without great difficulty. Jupiter, is very bright, and is low in the west by 9:30 PM. It is located in the constellation of Leo the Lion.

Venus is the bright star-like object in the East Northeast before Sunrise. However, due to its brightness, it is still visible after 5:30 in the morning. Just below Venus you can locate the planet Saturn, which will reveal its rings in a telescope of at least 30 power.

Also during the spring, look for the Big Dipper high overhead in the north, and slightly towards the west. Using the two stars on the end of the cup, draw an imaginary line away from the top of the cup, and it will point you to the North Star known as Polaris.

In the northeast, the famous Summer Triangle is getting higher up in the sky each night. It is marked by the three bright stars of Vega, Deneb, and Altair. They are the brightest stars in the constellations of Lyra the Harp, Cygnus the Swan, and Aquila the Eagle. The Summer Triangle is high up in the east by 10 PM.

Tomorrow after midnight, begin looking for the annual return of the Perseid Meteor Shower. The best time for viewing is around 4 AM, high up in the Northeast. The Perseids should produce around 60 meteors per hour. Tomorrow morning, while looking for the Perseids, look for the Waning Crescent Moon, surrounded by bright Venus and Saturn.

Public Programs at the Suits-Buech Planetarium at the Schenectady Museum are on Saturdays and Sundays at 1, 2, and 3 P. M. The 1:00 program is Visit to the Moon, a program for young people. At 2 P. M. is W S K Y, a program about almost everything in the universe, revolving around a fictional radio station. And at 3 P. M. is a live narration of the summer sky. Updates from the Cassini Spacecraft on its way to Saturn will also be presented.

Observe the last quarter Moon on August 7^th. The New Moon will occur on August 15^th, the First Quarter Moon on August 15^th and the next Full Moon on August 29^th.

Venus is a spectacular Morning Star for both the unaided eye and telescope in August. The planet rises in the east-northeast long before the first light of dawn.

All month Venus stands at almost exactly the same spot above your early-dawn landscape. Can you keep it in view all the way to sunrise, or even later?

Saturn rises around first light of dawn at the beginning of August. Scan just above the horizon very far to Venus’s lower left. Although Saturn is much dimmer than Venus, it easily outshines the Gemini stars Pollux and Castor poised not far to its upper left. During August Saturn and Gemini rise higher and higher, sliding towards Venus. If you get up early in the morning, watch the gap between the two planets dwindle all month. On the morning of August 31^st Venus and Saturn appear at their closest together (two degrees apart, a finger’s width at arm’s length), making a glorious pair.

The Moon hangs above Venus on the morning of August 11^th and left of Venus on the 12^th. The next morning, the lunar crescent is positioned between Saturn and the Gemini stars Pollux and Castor.

The Perseid meteor shower arrives in a dark, moonless sky this year, peaking on the morning of August 12^th. You can see a few Perseids as early as 10:00 p.m. on the evening of the 11^th, but the shower does not really get under way until after midnight, when the constellation Perseus climbs high in the northeast. If you have a dark sky, you may see a meteor a minute on average during the early-morning hours. The meteors will appear anywhere in the sky at random, so simply watch whatever part of your sky is darkest. But their direction of flight is always away from Perseus.

Dudley Observatory Sky-Watch Line for Wednesday August 18, 2004 by Michael Molitor

Sunset is at 7:52 pm, with the end of evening twilight occurring at 9:39 pm. Morning twilight begins at 4:20 am with sunrise at 6:07 am Thursday. The waxing crescent Moon is 10% illuminated and sets by the end of evening twilight.

With the exception of brilliant Venus, no planets are easily visible to the naked eye tonight. Shining at magnitude –4.3, Venus is 24 arc-seconds across and 50% illuminated. It rises in the east at 2:28 am and remains visible through morning twilight, being nearly 40 degrees above the horizon at sunrise

Viewers with access to a telescope and a little perseverance may find two additional planets Uranus and Neptune. These planets are visible all night, low in the southern sky. The best view of Neptune will be glimpsed around midnight, when the planet will then be at its highest due south, but still only 30 degrees above the horizon. Uranus is due south around 1:30 am Thursday morning and 37 degrees above the horizon.

Both Neptune and Uranus are challenging to identify, because they are small faint targets. With an apparent diameter of slightly less than 4 arc-seconds, Uranus shines at magnitude +5.7 and is located half of a degree northwest of the star sigma-Aquarius. Neptune at magnitude +7.8 and only slightly more than 2 arc-seconds across, is located a half degree northwest of the star theta-Capricorn. A good locator chart, or a properly aligned computerized telescope, is essential for hunting down these planets. Astronomy magazine and Sky and Telescope magazine have good locator maps and are available at most libraries. Or, use the magazines’ websites on-line. If you are not certain that you have located Neptune or Uranus, carefully draw a sketch of the stars that you see in the telescope eyepiece, along with the location of the suspected planet. Then view the same location of the sky, a day or more later. If you were correct in identifying the planet, its position should have changed relative to the more distant, “fixed” stars.

Once you have identified these distant worlds consider the circumstances surrounding their discovery. All the planets that were known since ancient history - Mercury, Venus, Mars, Jupiter and Saturn - are all bright and visible without optical aid. It took the invention of the telescope to find the faint distant worlds of Uranus and Neptune. Think of how William Herschel must have felt when he discovered Uranus in 1781 using his 7-inch telescope. Or, consider the exciting story of Neptune which was predicted to exist before it was ever observed. It was first seen by Johann Galle in 1846, exactly where John Couch Adams and Urbain Leverrier predicted that the planet should be. Today, the hunt for planets continues, except that the focus has shifted to looking for them circling distant stars.

Here’s hoping your hunting of the elusive planetary targets in our solar system is equally satisfying!

Skywatch Line for Friday, August 20, through Sunday, August 22, 2004 by Alan French

The Moon is moving toward Full and is back in the evening sky. The Sun sets near 7:50 PM each evening this weekend, and you'll find the Moon in the west-southwestern sky after sunset. On Friday night it will be a fat crescent, and on Sunday night it will be near first quarter and close to half sunlit. The Moon sets at 10:03 on Friday night and at 10:28 on Saturday night; so much of these nights will be dark and Moon free.

Weather permitting the Albany Area Amateur Astronomers will host public star Parties this coming weekend. At Star Parties a variety of telescopes are set up for your viewing pleasure, providing views of galaxies, star clusters, nebulae, and pretty double stars. During the early part of the star party, the amateur astronomers typically point their telescopes at some of the best celestial showpieces. Later on, they will be happy to take requests - provided, of course, the object is above the horizon and visible in amateur telescopes. Early arrivals will also have a view of the Moon, but it will set early enough to provide the dark skies best for observing faint nebulae and galaxies.

Friday night's program is at the George Landis Arboretum in Esperance, and begins at 9:00 PM. If you enter Esperance traveling west on Route 20, watch for the arboretum sign on your right, immediately after crossing the bridge over the Schoharie River. After taking the right, follow the signs to the arboretum. Continue up the hill past the main parking area and farmhouse, and turn right into the Meeting House drive as you reach the top of the hill.

Saturday night's Star Party is in Indian Meadows Park in Glenville, also beginning at 9:00 PM. Indian Meadows Park is off of Droms Road in East Glenville, and is marked by a large sign. After passing the park buildings, bear left at the fork in the road, and continue to a gravel parking lot on your left. The telescopes are set up beyond the gravel parking lot.

When you are inactive and standing under the clear night sky, it feels 10 to 20 degrees cooler than the actual temperature. It is better to have a few extra cloths on hand than to leave early because you are too cold.

There is no admission charge and all ages are welcome. You are welcome to stay as long or as briefly as you wish. Star Parties are canceled if the skies are mostly cloudy. Call Alan or Sue French at 374-8460 for more information.

The Sun sets tonight at 7:44, with night falling at 9:28 PM. Dawn breaks at 4:28 tomorrow morning, and ends with sunrise at 6:12.

As the Sun sets, the First Quarter Moon is found, due south, in the constellation Scorpius. The Moon’s brightness hides many dim objects in the area, but not planets.

Jupiter can be found in the West, just after Sunset. The giant planet is ending its appearance in evening skies. Jupiter is the brightest object in that part of the sky, just under Leo’s tail. However, the planet is quite low, so the observer must work quickly. After Jupiter sets, there are no easy planets in tonight’s sky. Neptune resides in Sagittarius; Uranus inhabits Aquarius. Pluto is found in Ophiuchus. Uranus and Neptune can be found with binoculars; but the observer needs patience and detailed charts.

Pluto was the last planet to be found in the 1930’s. Clyde Tombaugh used a major telescope to photograph the skies, and then searched thousands of images until Pluto was found. Today, moderate sized amateur equipment can spot the planet, but it appears as a dim dot amid many others.

Two bright planets grace the eastern pre-dawn and dawn skies. Venus rises first. It is the brightest object just below the twin stars of Gemini. Venus is intensely bright, due to its extensive cloud cover. Observed in strong binoculars or any telescope, this twin of Earth appears over half illuminated.

Saturn is now the subject of intense interest since the Cassini space probe just arrived there. Already there are discoveries. Newspaper reports indicate that Cassini found two new satellites to Saturn, bringing the total to thirty-three. However, Jupiter is still the champ, with sixty-one moons to its credit. However, Cassini is very early in its mission, and more moons may be found. Both Venus and Saturn are well up by the first light of dawn, and will be visible until Sunrise overwhelms them.

Skywatch Line for Tuesday, August 24th, 2004, by Steven Russo Planetarium Manager of the Suits-Bueche Planetarium at the Schenectady Museum.

The sun will set tonight in the west northwest at 7:44. It will rise in the east northeast on Wednesday at 6:14 and set in the west northwest at 7:42. The Moon is currently in First Quarter phase, and will set after midnight tonight. It will rise at around 5:20 tomorrow evening.

Planet viewing is now at a minimum, and your best view of these solar system objects is in the morning sky.

Sunrise. However, due to its brightness, it is still visible after 5:30 in the morning. Just below Venus you can locate the planet Saturn, which will reveal its rings in a telescope of at least 30 power.

In the evening sky, look for the Big Dipper in the northwest sky. Using the two stars on the end of the cup, draw an imaginary line away from the top of the cup, and it will point you to the North Star known as Polaris.

The famous Summer Triangle is just about overhead by 10:00 PM. It is marked by the three bright stars of Vega, Deneb, and Altair. They are the brightest stars in the constellations of Lyra the Harp, Cygnus the Swan, and Aquila the Eagle. Rising in the north east, you can spot the Andromeda Galaxy. Appearing as a dim smudge, it is actually a spiral galaxy with about 300 billion stars. The light that left Andromeda has traveled 2 million years to reach your eyes.

With the Moon gibbous at two days past first quarter, the Milky Way, arching overhead in the summer sky, will be difficult to see. But there is still much to see.

Almost directly overhead are two first magnitude stars. The brighter of the two is Vega, or Alpha in the constellation Lyra, the Ly re. Facing south, Lyra appears as a small constellation consisting principally of a small parallelogram of stars together with Vega to the upper right. Vega is, to say the least, unmistakable being somewhat bluish and one of the brightest stars visible to northern observers.

The dimmer star, by approximately one magnitude, is Deneb, or Alpha Cygni in the constellation of Cygnus the Swan. Although it appears somewhat dimmer than Vega, intrinsically it is much brighter but appears dimmer because it is so much further away. While Deneb represents the tail of the swan, most people see this area of the sky as the Northern Cross, with Deneb at the top of the cross. Following the length of the cross, from northeast to southwest at around ten at night, the bottom of the cross is represented by Albireo, considered one of the most beautiful double stars in the entire sky, the primary star of the pair being yellow and the companion being greenish or bluish. Albireo lies slightly to the left (that is east) of an imaginary line from Vega to the bright star Altair in the constellation Aquila, the Eagle. Vega, Deneb and Altair form what is commonly referred to as the summer triangle, a name popularized by Sir Patrick Moore, who has been popularizing amateur astronomy for decades.

Rising in the east is the constellation of Pegasus, the Horse, a harbinger of autumn. The constellation’s main component is made up of what is commonly referred to as the Great Square of Pegasus, although technically one of the stars making up the square is actually in the constellation of Andromeda. The square is rather large and the four stars not exceptionally bright, so it is not readily recognized at first. A planisphere or very simple sky map will make finding it easy.

Newcomers and initiates are well advised to buy a planisphere in order to learn the constellations. It’s a simple device which operates by rotating a map of the entire sky according to the date and time. That and attending a star party or two will enable any novice to learn his or her way around the sky.

Observe the Full Moon on August 29th and the Last Quarter Moon on September 6^th.

Observe the most beautiful double sky of the summer sky called Albireo, in the constellation Cygnus the Swan. Find the Summer Triangle, stretching from high overhead off to the south. The eastern most of the stars is Deneb, which sits at the top of the Northern Cross (or, if you prefer, at the tail of Cygnus the Swan). The cross runs to the south and west, going right between the other two stars of the triangle, Vega and Altair. Albireo is the star at the foot of the cross.

In the finder scope: Albireo is quite easy to find, being the brightest star in the immediate neighborhood. In the telescope: the double star is easy to split, even at moderate powers, and the color contrast is striking.

Albireo is the standard against which all other doubles are judged. The attractions of this double star are many. First, it is quite easy to find. Second, it is well separated, and therefore easy to split; yet the two components are close enough together and close enough in brightness that they make a nice pair. But the biggest attraction of this pair is the color contrast. If you have ever doubted that stars have colors, this pair should remove any doubt.

The colors stand out best at low to medium magnification, in a small telescope. A little bit of sky brightness (twilight, or a Full Moon) can actually help your eye appreciate the colors. Some observers like to look at these stars very slightly out of focus to emphasize the colors.

Albireo is made up of a giant orange Spectral type K) star, orbited by a hot blue (spectral type B) star. Star B lies at least 4,500 AU away from A. AU stands for one Astronomical Unit or the distance from the Sun to the Earth. These two stars are 4,500 times farther away from each other than we are from the Sun. It must take about 100,000 years to complete an orbit about it. The two stars lie 400 light years away from the Earth. You are looking at the stars as the appeared in the year 1604 on Earth.

To the delight of casual skygazers and amateur astronomers, we have finally been treated to some clear nights. Unfortunately for those seeking views of what are termed deep sky objects – celestial sights that lie outside our solar system, including gaseous nebulae, star clusters, and galaxies – bright moonlight will interfere with the views this weekend.

The Moon is now approaching full, and will rise around sunset over the weekend. On Friday night, it will rise at 6:45 PM, a bit more than one half hour before sunset. The Moon now rises about thirty minutes later each night, so on Saturday night the Moon will appear above the eastern horizon at 7:21 PM, a mere 15 minutes before sunset. By Sunday night, the Moon will rise at 7:50 PM, almost 30 minutes after sunset.

The Moon will be at Full 10:22 PM on Sunday night. The Full Moon of August is called the Green Corn Moon or Grain Moon. The full phase is not a good time to see the craters and mountains on the Moon because the sunlight is coming from directly behind us, so we do not get the long shadows that can bring out such features in bold relief. This, however, is an excellent time to see the seas, which appear as darker regions of the Moon. They show up very well in virtually any pair of binoculars, especially if you can put them on a steady mount. The seas or Maria are lava plains – huge regions of basalt. If you do look at the Moon through binoculars, also look for "rays" crossing the surface of the Moon. These are made up of material ejected out of some of the huge craters when they were formed by explosive impacts of large meteors or asteroids.

If you up in the early dawn hours an hour or two before sunrise, be sure to look toward the eastern horizon. There you will spot beautiful Venus shining in all her glory. Here extreme brightness is due to her relative closeness to our Earth and the reflective clouds that cloak her from our view. Venus in now near ringed Saturn. On Friday night, Saturn will be to the lower left of Venus, but the pair is rapidly moving closer together. On next Tuesday morning, they will be separated by only two degrees – four times the apparent size of the Moon. Let us hope for some clear morning skies so we can watch this duo move closer!