This is the Skywatch Line for Monday and Tuesday, September 29th and 30th.
by Joe Slomka

The Sun sets at 6:39 PM, with night falling at 8:14. Dawn breaks at 5:16 and ends with sunrise at 6:51.

As the Sun sets, two bright objects attract our attention to the southern sky. Jupiter is highest and almost due South. It is quite bright and easily seen as the sky darkens. Binocular users see two moons on each side of Jupiter. Telescope observers can watch the Great Red Spot, a large storm, cross Jupiter's face at 9:32 PM.

Venus is more brilliant, but lower in the southwest. Venus is slowly emerging from the Sun's glare and should be high enough for observation. A telescope reveals Venus as eighty-six percent illuminated, contrasting with Jupiter's almost one hundred percent. Venus is now sixty-six degrees from Jupiter, but will close the gap in coming months.

The first light of Dawn brings the planet Saturn into view, low in the East. Like Venus, Saturn is slowly emerging from the Sun's glare. Telescopic observers will see a much fainter planet, due to the shrinking angle of its ring system. The rings continue to close through the rest of the year.

Shortly after nightfall, the constellation Perseus appears moderately high in the northeast. The hero has one leg longer than the other. The brightest star in the short leg is Algol. Algol, the “Demon Star,” varies its light every 2 days, 20 hours and 49 minutes. It fades from second magnitude to third – easily seen by the naked eye. Two hundred twenty-five years ago, John Goodricke theorized that a dimmer star was partially eclipsing a brighter star. In 1889, the new technique of spectroscopy verified this theory. The main star is one hundred times the Sun’s luminosity. The eclipsing star is actually slightly brighter than our Sun. There is a third star that orbits the system once every 1.8 years, but plays little part in the occultation. The system is about 100 light years away and the most easily studied “eclipsing binary.” The eclipse is deepest at 9:32 on Monday night; Algol takes about five hours to regain its normal brilliance.

Clear Skies
Joe Slomka

 

This is Dudley Observatory's Skywatch Line for Friday, September 26, though Sunday, September 28, written by Alan French.

The Moon will be new very early this coming Monday morning, so the skies over the weekend will be essentially moonless. A very old Moon will rise just before sunrise on Saturday and Sunday mornings, but will probably be too close to the Sun to see on Sunday.

The very thin crescent Moon will be a fairly easy target on Saturday morning, but you'll need a good view to the east and good timing. Look for the crescent due east and a bit less than ten degrees above the horizon at 5:45 AM. As morning twilight grows, the Moon will rise higher, soon losing the battle with the brightening eastern skies.

The bright yellowish star to the left of the Moon on Saturday morning is the planet Saturn, now emerging into the morning skies and rising a bit earlier each morning. By mid-December Saturn will rise just after midnight, and will be high in the southern sky as morning twilight begins.

On Sunday the Moon will not rise until 6:04 AM, with the Sun following only 37 minutes later. The Moon will be two degrees above the horizon by 6:20. If you have a good view of the eastern sky and it is free of clouds and haze, there is a chance you will spot this very old Moon.

Weather permitting, the Albany Area Amateur Astronomers will hold public star parties at 8:00 PM on Friday, September 26, and Saturday, September 27, at George Landis Arboretum in Esperance. At star parties the amateur astronomers and Dudley Observatory's Rising Star Interns set up a variety of telescopes to show guests sights in the night sky. The planet Jupiter is visible now, and telescopes will reveal its main cloud bands and its four brightest moons. Telescopes will also show multiple stars, star clusters, nebulae, and distant galaxies.

To reach the arboretum, take Route 20 toward Esperance. Just after you cross Schoharie Creek, turn right. There is a large green sign for “George Landis Arboretum” at this intersection. Continue to follow the signs for the arboretum for one and a half miles. Once you reach the arboretum farmhouse on the right and main parking area on the left, continue up Lape Road to the top of the steep portion of the hill. Turn right into the driveway to the Meeting House.

The nights are turning cooler, and it is easy to get chilled standing under a clear night sky, so dress warmly and bring some extra warm clothing. The star parties are canceled if the skies are mostly cloudy. Call 374-8460 late in the afternoon if in doubt, or for more information.

Dava Sobel will give the first lecture in Dudley Observatory's Skywatch Lecture series at 8:00 PM, on Thursday, October 9, in the GE Theater at Proctor's. For more information visit www.dudleyobservatory.org. Tickets may be purchased at the Proctor's box office or at their web site, www.proctors.org.

 

Skywatch line for Wed. & Thurs., September 24 and 25, 2008
by Ray Bogucki

Facing north at nightfall, one sees, to the right of Polaris, the North Star, the familiar "W' asterism of Cassiopeia climbing in the northeast. One can use the "W" to find another famous object, the Great Andromeda Galaxy. Using the upper three stars of the "W" as an arrowhead pointing to the right, follow an imaginary line to the right a little longer than the length of the "W" itself, to a bright, second magnitude star, beta-Andromedae. About one binocular field to the left of this star is another, somewhat fainter star, and still a little farther left is a third star. Just above this third star is a fuzzy elliptical patch of light just visible to the naked eye in a dark sky. This is the Andromeda Galaxy, probably the most distant galaxy we can see without optical aid. This galaxy played a critical role in astronomers' understanding of the nature and size of the universe.

In 1784, the very young English astronomer, John Goodricke, discovered that a star in the constellation Cepheus varied in brightness with a very constant period of about 5 1/2 days. Many other stars of this type were soon discovered with different periods but with the same characteristic shape of their light curves, which became known as a Cepheid Variable stars.

Over a century later, in 1908, Harvard Observatory astronomer, Henrietta Leavitt, was studying Cepheid Variable stars in the smaller Magellanic Cloud, a diffuse star cloud visible from the southern hemisphere. She discovered that the apparent magnitudes of these stars were related to their periods of light variation; the brighter the star, the longer the period. Since the ratio of the apparent magnitude of a star to its absolute magnitude is a function of distance, and since all of the stars in the Magellanic Cloud lie at about the same distance from earth, Ms. Leavitt had actually discovered that the absolute magnitude of a Cepheid Variable star can be determined by its period. This discovery provided astronomers with a valuable yardstick for measuring the distance of any Cepheid Variable by measuring its apparent magnitude and its period.

In 1917, Harvard astronomer, Harlow Shapley, used this method to measure the distances and spatial distribution of globular clusters in our galaxy. He found that most globular clusters did not reside in the plane defined by the spiral arms of our Milky Way Galaxy but were arranged in a roughly spherical shape around our galaxy's central bulge. At that time, most astronomers believed that the fuzzy patches of light were clouds of stars or gas that resided in our own galaxy which was thought to constitute the entire known universe. But in 1923, Edwin Hubble found Cepheid Variables in the Andromeda Galaxy, and, using Ms. Leavitt's yardstick, determined that this cloud was actually 2 1/2 million light-years away -- far outside of our galaxy. Later, studying more distant galaxies in the same way, he discovered that the more distant a galaxy was, the faster it was receding from us, thus giving us the concept of an expanding universe.

 

This is the Skywatch Line for Monday and Tuesday, September 22nd and 23rd.
by Joe Slomka

The Sun sets at 6:52 PM, ending with nightfall at 8:27. Dawn breaks at 5:08 and ends with sunrise at 6:44.

As the Sun sets, two bright planets attract attention. Jupiter is bright and easily spotted low in the southeast. It appears near teapot-shaped Sagittarius until it sets after midnight. Jupiter's four famous moons produce endless combinations for the observer. For example, binocular users can see the moon Io appear from behind Jupiter at 8:04 PM Monday.

Venus blazes low in the southwest shortly after sunset. If Venus is too low to overcome obstacles, it becomes easier to spot as the month progresses. Venus displays phases like the Moon. A telescopic view shows Venus eighty-eight percent illuminated. Try to observe Venus often and track how its shape changes.

The Last Quarter Moon rises after midnight on Tuesday and resides between Gemini's legs. Wednesday morning finds it between Gemini and Cancer.

The hour before sunrise finds the Moon being joined by Saturn. Like Venus, Saturn struggles to escape the Sun's pre-dawn glare. Again, Saturn is quite low in the sky, and may be blocked by hills or trees. As the month progresses, Saturn rises earlier and is better observed. If you do see Saturn, notice how its famous ring system now appears very thin, as opposed to the last view a few months ago. If you observed Saturn at that time, it was near Regulus, the brightest star in Leo. Now, Saturn is near the lion's rear legs.

Last week's Skywatch Line drew attention the Harvest Moon and defined it as the Full Moon closest to the Autumnal Equinox. Monday at 11:44 AM, the Sun crossed the imaginary equator in the sky. This intersection of the Sun's path and the Celestial Equator is called the Autumnal Equinox and brings Fall to the Northern Hemisphere and Spring to those south of Earth's Equator. Daylight drops off dramatically. The Sun sets earlier and rises later. The Sun keeps heading lower in the sky until it hits bottom at the Winter Solstice, when the upward cycle begins.

Clear Skies
Joe Slomka

 

This is Dudley Observatory's Skywatch Line for Friday, September 19, through Sunday, September 21
written by Alan French.

We have chances to see the International Space Station, commonly known as the ISS, each evening over the weekend, with two passes on Sunday night. The forecast is for generally clear skies, so perhaps you can catch the ISS each night.

We see the ISS because it is still up in sunlight while we are down in the Earth's shadow. Because the ISS is large and reflects a lot of sunlight, it appears brighter than the stars in the night sky. For three of the four passes we will get to see the ISS fade from view as it moves into the Earth's shadow.

On Friday night the ISS will first appear at 8:00 PM rising up from the south southwestern horizon. The path of the space station will then take it just below brilliant Jupiter, the brightest starlike object in the night sky. Does the ISS look brighter than Jupiter? The ISS will be highest at 8:02:42 PM when 31 degrees above the southeast horizon. Less than a minute later it will begin moving into the Earth's shadow and fade from view in the east southeast.

Saturday night's pass will be highest and brightest, and the ISS will move into the Earth's shadow while still quite high in the sky. Look for it coming up from the west southwestern horizon just after 8:26 PM. It will be highest just after 8:29 when it will appear 76 degrees above the north northwestern horizon – essentially overhead. Thirty seconds later, as it leaves the constellation Cepheus headed for the familiar “W” of Cassiopea, the ISS will begin moving into our Earth's shadow and will fade from sight. How far can you follow the station after it begins fading?

The first pass on Sunday night will be early under bright twilight skies. The ISS will move up from the south southwestern horizon at 7:17:40 PM, will be highest at 7:20:24 when 36 degrees above the southeastern horizon, and will vanish as it moves below the east northeastern horizon just after 7:23.

Sunday's second pass will begin at 8:53:07 PM when the space station rises up from the western horizon. It will appear highest at 8:55:33 when 29 degrees above the north northwestern horizon and moving through the handle of the Big Dipper, and will immediately begin fading from view as it enters the Earth's shadow.

Next weekend the Albany Area Amateur Astronomers will hold public star parties at George Landis Arboretum in Esperance. The star parties will begin at 8:00 PM on Friday, September 26, and Saturday, September 27, and are free and open to all. A variety of telescopes will be set up in the Meeting House field, which is up Lape Road past the farmhouse and main parking area. Star parties are canceled if the skies are mostly cloudy. Call 374-8460 to verify the star party is being held or for further information.

 

Skywatch line for Wed. & Thurs., Sept. 17 and 18, 2008:
by Ray Bogucki

Earlier this year, on June 21, the Sun reached its farthest point north of the celestial equator at the summer solstice. At this point, the Sun reversed direction and slowly began its six-month southward journey. Next Monday, Sept. 22, the Sun will cross the celestial equator at the autumnal equinox, halfway through its journey to its southernmost point at the winter solstice on Dec. 21. The speed of its southward motion reaches a maximum at the equinox, and this is noted by people who observe that the Sun sets noticeably earlier each day and the length of each day is rapidly growing shorter. For example, in the 3 week period following the summer solstice, we lost about 14 minutes of sunlight, while in the 3 week period centered on this equinox, we will lose well over an hour of sunlight.

The equinoxes and solstices have been recognized as special times and celebrated as far back as the beginnings of human history. In all the inhabited parts of the planet, the Sun, next Monday, will rise due east, and set due west on the theoretical horizon just twelve hours later. This explains the origin of the Latin word "equinox" which means "equal night".

An exception to this behavior occurs at the uninhabited poles of the planet. At the North Pole, an observer would see the Sun circling on the horizon in a clockwise manner. By the next day, the Sun, still circling, would slowly drop below the horizon, not to appear again for 6 months. At the South Pole, the Sun would circle the horizon in a counter clockwise manner, and on the next day, it would circle a little higher, beginning a 6 month period of constant sunshine. It is only on the precise days of the spring and autumnal equinoxes that observers at the opposite poles could see the Sun at the same time.

The effects of the Earth's planetary motions as seen from different places on the Earth's surface are fascinating. At the equator, the Sun rises and sets straight up and down at 90 degrees to the horizon. This makes for very short periods of morning and evening twilight. But at far north locations, such as Stockholm, Sweden, the Sun sets at a very shallow angle so that one can easily read a newspaper outside at 11 p.m. on a slowly dwindling, long summer evening.

 

This is the Skywatch Line for Monday and Tuesday, September 15th and 16th.
by Joe Slomka

The Sun sets at 7:03 PM, with night falling at 8:41. Dawn breaks at 4:59 AM, with sunrise taking place at 6:36.

At sundown, two bright objects blaze in the southern sky. Jupiter is highest and almost due South. It is easy to spot in the twilight, and best observed between nightfall and midnight. Monday evening at about 7:31, binocular observers can watch the moon Io reappear from behind the giant planet. Tuesday night has the moon Ganymede's shadow cross Jupiter, beginning at approximately 10:40 PM - as seen in a telescope.

Venus struggles to be seen, low in the southwest, by climbing above the twilight. Though the brightest object in the sky, it is easily obscured by trees or buildings. If your horizon is clear, far fainter Mars lies two degrees to the West. Both planets should fill the same binocular or finder field. Both Venus and Mars set by 8:05 PM. Venus slowly ascends higher over the month, leaves Mars behind and heads toward Jupiter.

Just as Venus struggles to be seen in twilight, Saturn emerges in brightening dawn skies, low in the East. Saturn rises at 5:41 AM; so, observers have about forty-five minutes before the Sun's glare takes over. If efforts are unsuccessful, Saturn rises earlier and higher in coming months.

The Moon turned "Full" this morning and rises at 7 PM. This is the famous Harvest Moon, defined as the Full Moon nearest the Autumn Equinox. The Harvest Moon is special because the fall harvest could be conducted without daylight. Usually the Moon rises about an hour later each night. However, due to the shallow Moon’s path in the sky, called the ecliptic, this time of the year has the Moon rising between twenty minutes and a half hour later. Pre-tractor farmers had the Moon to work by. This grace period lasts only until September 21st, when the moonrise gradually lengthens to its normal interval.

Clear Skies
Joe Slomka

This is Dudley Observatory's Skywatch Line for Friday, September 12, through Sunday, September 14, written by Alan French.

The Moon was at first quarter on Sunday so a waxing gibbous Moon will dominate the evening sky over the weekend. The Moon will be full early Monday morning and a lovely Harvest Moon will rise a little north of due east almost exactly at sunset on Monday night.

The weather forecast says we will not have any clear skies this weekend, so we'll talk about a tool and two books of interest to skywatchers. An essential tool is a planisphere. This has a rotating circular map of all the constellations visible, with a portion of the map visible through a window in an outer sleeve or cover. The outer part of the map is marked with dates, and the fixed sleeve is marked with times. By rotating the star map to the current date and time, you get a view of the sky visible to you. It can easily be set to show the sky at any time on any night.

Planispheres have to be specific to your latitude. As you move farther south, stars farther south and always below the horizon from our norther latitude become visible. As you move farther north, stars in the southern part of the sky disappear and never rise into our sight. We live just shy of 43 degrees north, so pick the planisphere that covers our latitude – usually one marked “40 to 50 degrees north latitude.” If it is offered in a local bookstore, there is an excellent chance it is for use here.

Planispheres don't usually include a provision for daylight savings time, so simply subtract an hour to the current time when you set the planisphere. If you are out at 10:00 PM EDT, set the planisphere for 9:00 PM EST. Because the planets wander among the stars, planispheres do not include the planets.

As you probably know, it takes your eye time to adjust to darkness when you go outside stargazing. The eye's pupil opens wider to admit more light, and a slower chemical change greatly increases the eye's sensitivity to light. The use of a white light to view your planisphere will immediately reverse these changes. To maintain your dark adaption and still see your planisphere, use a dim red light. The light should be just bright enough to allow you to see the planisphere with your fully dark adapted eye. Most amateur astronomers buy a variable brightness red LED light made with them in mind, but you can make one with red construction paper or plastic.

If you want to another way learn the constellations, or improve your knowledge of them, H.A. Rey's “The Stars (A New Way to See Them)” and “Find the Constellations” remain excellent guides. “Find the Constellations” is available new for about $10, but the new printing of “The Stars” is not out yet. It has been reprinted many times, however, and is widely available used. Some bookstores may still have the previous edition.

The Albany Area Amateur Astronomers will meet at 7:30 PM on Tuesday night at the Schenectady Museum. Meteorologist Steve Caporizzo will be their guest speaker. Club meetings are free and open to everyone. Perhaps we'll see you there.

Skywatch line for Wed. and Thurs.  September 10 and 11, 2008:
by Ray Bogucki

 

  Jupiter remains as the undisputed king of the planets, blazing at a magnitude of minus 2.5 low in the south at night fall.  Unfortunately, Jupiter is currently traveling slowly along the part of the ecliptic which is farthest south of the celestial equator so that it never gets very high in the sky and remains in the turbulent air just above the horizon.  Still, the giant planet and its four Galilean moons provide a favored target for evening observers.

 

  Last month, we described the glorious choreography of the planets Saturn, Venus and Mercury, constantly shifting positions very low in the west with Mars observing its siblings from above and to the left.  A week ago, the Earth's orbital motion around the Sun carried Saturn behind the Sun at conjunction, rendered invisible in the Sun's glare.  In two weeks, our orbital motion will place Saturn far enough west of the Sun that it will be the only, lonely planet visible in the early morning twilight, rising an hour before the Sun to entertain early risers.

 

  Meanwhile, back in the western sky right after sunset, the two inner planets, Venus and Mercury, have caught up with Mars and a new pas de trois is occurring very low on the western horizon.  As with last month's planetary ballet, it will be necessary to use binoculars and find a viewing site that is unobstructed to the west.  Even better, find a high hill with a valley dropping off to the west!  Tonight, Wednesday, Venus is approaching just about one Moon-width above Mars.  Tomorrow night, it will make its closest approach -- about one half a Moon-width above Mars, with Mercury just a little below and to the left of the tight pair.  The bright star Spica, in the constellation Virgo, is just to the left of the pair. 

 

   All through the next week, these four points of light will form ever changing quadrilateral figures until, one week from Thursday, they will form a slightly distorted square, standing on a corner, with bright Venus at the top, and directly above Mercury at the bottom.  Spica forms the left point and Mars the right.  Watching this choreography will prove very challenging, even with binoculars, but brilliant Venus is relatively easy to find and knowing the precise pattern, as with the square next week Thursday, will help you find the others.  In two weeks, Mercury will become invisible in the Sun's glare and by the end of September, Mars and Spica will also disappear.  But Venus will continue to climb higher in the evening sky until, at Christmas, it will replace Jupiter, setting in a black sky, almost four hours after sunset and two hours after Jupiter sets.