|
Dudley Observatory
Supporting research and education in astronomy, astrophysics, and the history of astronomy |
|
|
Skywatch
April 2008
(newest at top)
Skywatch line for Wed., April 30 and Thurs., May 1, 2008:
by Ray Bogucki
The coming week presents a number of interesting sights for skywatchers. On Thursday, Saturn's rings will be tilted at 9.9 degrees from edge-on, the largest tilt the rings will show until the year 2010. Saturn has been close to the bright star, Regulus, in Leo the Lion, for the past month, moving in slow retrograde motion as the Earth overtook and passed it last February. On Saturday, Saturn will appear stationary against the background stars as our orbital motion carries us directly away from the giant planet. Saturn will then resume its normal slow eastward motion through the stars which will finally carry it away from Regulus.
In the evening sky, Mercury is beginning its best evening apparition for this year. On Friday night, you can find Mercury low in the west about 45 minutes after sunset. It will appear about 4 degrees below the well known star cluster, the Pleiades, which should easily show up in binoculars in the darkening twilit sky. Each evening, Mercury will climb noticeably higher in the evening sky. By a week from now, it will be setting two hours after the Sun in a fully dark sky. On Tuesday evening, Mercury, still close to the Pleiades, will be joined by the very young, thin crescent Moon to present an elegant gathering of the Moon, the planet, and the star cluster. Incidentally, the Moon, which passes in front of the Sun in its New Moon phase early Tuesday morning, will be at perigee, its closest approach to the Earth a few hours later. The combined gravitational force on the Earth's oceans of the Sun and the perigean Moon pulling from the same direction, will cause unusually high tides on Tuesday and Wednesday.
On Monday, May 5, the eta-Aquarid meteor shower will peak near midday. Because the meteors persist for several days, they should be visible very early Monday and Tuesday mornings. The best viewing will be after 2 a.m. at which time the radiant, the point from which all the Aquarid meteors appear to originate, rises above the horizon. Fortunately, because the New Moon occurs on Monday, there will be no moonlight to interfere with a dark sky. A careful observer may see several dozen meteors per hour, usually moving very fast. The eta-Aquarid meteors are generated when the Earth passes through the cometary debris left in our orbit by the passage of Halley's Comet.
This is the Skywatch Line for Monday and Tuesday, April 28th and 29th.
by Joe Slomka
The Sun sets at 7:53 PM, with night falling at 9:42. Dawn breaks at 4:02 AM, and ends with sunrise at 5:51.
Shortly after sunset, three bright planets appear in a straight line across southwestern skies. Mercury is the brightest and the first to be seen, low in the West. This elusive planet is never far from the Sun and hugs the horizon above the sunset. Use binoculars to see a very bright star-like object. This is Mercury's best appearance of the season. Saturn and Mars are higher and take longer to appear. Mars remains in Gemini; at nightfall, it is found about five degrees from the similar looking star Pollux. Both share the same color and brightness.
Saturn lies only two degrees from the dimmer star Regulus. Saturn's ring system opens to ten degrees, the widest it will be until 2010. The rings are held in place by Saturn's gravity and its myriad moons, which "shepherd" ring particles together.
Tuesday's Dawn finds the Last Quarter Moon in the tail end of Capricornus; Wednesday morning finds it within Aquarius. Jupiter drifts between Sagittarius and Capricornus.
As night falls, the unmistakable shape of Leo, the Lion, dominates the evening sky. Leo is one of those constellations that look like its namesake. If one looks past Denebola, the Lion’s Tail, one sees a faint hazy cloud. Binoculars show it to be a galactic star cluster. This cluster is called Coma Berenices. Unlike most constellations, Berenice was not mythical figure. She was married to Ptolemy III of Egypt. When her brother-in-law involved the Pharaoh in a war, Berenice, like all wives, worried about her husband in battle. She vowed to Aphrodite that she would donate a lock of her hair if Ptolemy arrived home safely. He did; and she fulfilled her promise. One day the royal couple inquired of the court priest-astrologer what happened to her donation. He replied by pointing to hazy cloud in the sky and said the gods accepted her sacrifice. Berenice is famous for another reason; she is Cleopatra’s grandmother. The modern Libyan city of Benghazi bears a modified version of her name.
Clear Skies
Joe Slomka
This is Dudley Observatory's Skywatch Line for Friday, April 25, through Sunday, April 27, written by Alan French.
The Moon was full last Sunday so a waning gibbous Moon rises after midnight and the early evening hours are dark and moonless. On Sunday morning the Moon will be close to Jupiter, which will be the brightest “star” near the lunar orb.
The International Space Station is the brightest man made satellite orbiting the Earth, largely because of its size. There are many other satellites visible crossing our skies, and anyone watching the skies regularly is bound to spot a few during the hours after sunset and before sunrise. We see them because they are still up in the sunlight when we are down in the Earth's shadow.
Sometimes we can see a satellite travel from horizon to horizon, but we can also catch satellites moving out of the Earth's shadow into the sunlight and becoming visible, or moving into the Earth's shadow and vanishing. On Saturday night we have a chance to see a satellite emerge from the Earth's shadow when well above the horizon. A satellite moving through our skies will move into our planet's shadow while high in the sky on Sunday night.
Saturday night's satellite is USA 129, used for Military Reconnaissance. It will appear as bright as the brighter stars in the Big Dipper, and will move out of the Earth's shadow and become visible at 9:24 PM. To see it emerge from the shadow look at the triangle formed by Saturn, Spica, the brightest star in Virgo, and Arcturus, the brightest star in Bootes. Watch the middle of this triangle as 9:24 approaches. After moving into sunlight, USA129 will pass through the handle of the Big Dipper, through the Little Dipper, and down past Cassiopeia.
On Sunday night we can watch the Upper Atmospheric Research Satellite, or UARS, move into the Earth's shadow and fade from view. It will appear brighter than the stars in the Big Dipper, but will not rival the brightest stars in the sky. The UARS will first appear moving up from the northwestern horizon at 9:26:22 PM. It will come up through Perseus and pass close by Capella, the brightest star in Auriga, and will be highest at 9:29:25. Just after passing through the triangle of stars that mark the rear quarters of Leo, the Lion, it will move into the Earth's shadow. How long does it take to vanish entirely?
Skywatch line for Wednesday & Thursday, April 23 & 24, 2008
by Ray Bogucki
Of the five bright planets, Venus is preparing to pass behind the Sun and is lost in the Sun's glare, Mars and Saturn are well placed for viewing in the evening, and Jupiter, which rises about 1 a.m., is viewable in the early morning sky. Mercury passed behind the Sun a week ago and is now beginning to appear low in the early evening western sky. Binoculars will help to find it just above the western horizon about a half hour after sunset. Mercury will rise higher and brighter in the western sky after sunset for the next couple of weeks and it will remain visible through most of the month of May.
Mars continues to fade as we draw away from it in our faster solar orbit. Its slow, eastward movement through the stars will carry it close to the bright star, Pollux, during the coming week. Currently Mars and Pollux have the same brightness - magnitude plus 1.2 - and they each show an orange tint, but for very different reasons. The star, Pollux, appears orange because it is a relatively cool star, while Mars, shining only by reflected sunlight, appears orange because its surface contains a significant amount of iron oxide, known as "rust" on planet Earth. Because they are just the same brightness, they suggest an interesting comparison. To your eye, or with optical aid, which object appears farther from pure white in color?
This is the Skywatch Line for Monday and Tuesday, April 21st and 22nd.
by Joe Slomka
The Sun sets at 7:45 PM, with night falling at 9:30. Dawn breaks at 4:17 AM, ending with sunrise at 6:02.
Mars appears high in the southwest shortly after sunset. Mars is a tiny red dot in Gemini, near the star Pollux. After nightfall, compare Mars with Pollux. Mars is a rusty red, while Pollux, in binoculars or telescope, appears yellowish. But, they are nearly equally bright. Mars is 1.1 magnitude, Pollux is 1.2. Can you see the difference? Mars continues its slow march across Gemini.
Saturn is also high in the southwest sky after sunset. Nightfall finds it close to Regulus, only two degrees away.
Saturn is ideally situated for observation of its famous ring system and several of its sixty moons. Astronomy web sites and magazines help the observer identify the satellites.
Mercury lies low in the West at sunset. It made a dash behind the Sun and now begins the best appearance of the year for Capital District observers. Mercury lies low, only five degrees above the horizon; but it will get better as the month progresses. Binoculars or telescope assist the observer in finding this famously elusive planet. As April progresses, Mercury will be better placed for observation.
The waning Moon rises about 9:30 PM and shines near the bottom of the diamond-shaped constellation Libra. Tuesday night, a slightly dimmer Moon hovers near the head of Scorpius.
Jupiter joins the scene at approximately 2 AM. It is found to the left of teapot-shaped Sagittarius. An ordinary pair of binoculars allows the observer to see the four Galilean moons. At this time, Jupiter has reached quadrature, which means that the planet lies at a ninety-degree angle from the Sun. It also means that it shadow eclipses some of the Galilean moons. Again, astronomy magazines and web sites assist the observer to discover the timing of these events.
Finally, Neptune is observable just above the tail star, Deneb Algiedi, in Capricornus. Neptune appears to the telescope as a blue-green dot above the much brighter star.
This is Dudley Observatory's Skywatch Line for Friday, April 18, through Sunday, April 20, written by Alan French.
The Moon will be Full at 6:25 Sunday morning, so the night skies over the weeked will be dominated by a bright Moon. The Full Moon of April is variously called the Egg Moon, Grass Moon, or Easter Moon.
Looking at the Moon at the same time each night over the weekend will provide a nice illustration of the Moon's relatively rapid motion eastward among the stars. The Sun now sets about 7:43 PM. If you look toward the southeast at 9:00 PM on Friday night, you will find a waxing gibbous Moon almost 25 degrees above the horizon. Spica, the brightest star in the constellation Virgo, will be to the moon's lower left.
On Saturday night at 9:00, the Moon will be almost full, and just 15 degrees above the horizon. Spica will then appear just above the Moon. With your eye alone, can you tell that the Moon is not really quite full?
By Sunday night, the Moon will be just past full, and will stand only a little over four degrees above the horizon and will be a bit farther east.
Most amateur astronomers – even lunar observers – tend to dislike the full Moon. Its light washes out the subtle nebulae and galaxies that are favored telescopic targets. Lunar features stand out in bold relief along the terminator, which is the sunrise or sunset line marching across the Moon. At full, the terminator runs around the limb or edge of the Moon, so craters and mountains on the visible face do not stand out. However, the albedo features – features that vary in the amount of light they reflect – stand out very well. Even the unaided eye can very easily pick out the darker, flatter Mare or “seas.”
The Mare are large, dark basaltic plains, and most can easily be identified with the eye alone. If you visit http://en.wikipedia.org/wiki/Lunar_mare you will find a map on the upper right side of the page that nicely identifies these features. Select the larger version of the map, print it out, and see what you can identify on the lunar orb. The orientation of the Moon varies as it crosses the sky, so you'll have to adjust the tip of the map to your view of the Moon.
Skywatch line for Wed. and Thurs. April 16 and 17, 2008:
by Ray Bogucki
Any longtime skywatcher can conjure up the memory of a late summer evening sky when the Milky Way rises dramatically from the northeastern horizon. It climbs straight up through Cassiopeia and crosses the zenith at the Northern Cross, then plunges down through Aquila the Eagle, brightening noticeably at the central bulge of our galaxy in Sagittarius at the southwestern horizon. Actually the central hub of our galaxy would appear even brighter if it were not partially obscured by vast clouds of dust and gas in the planar arms of the galaxy. Because the Sun, with its planets, is embedded in one of the spiral arms of our flat, disk-like galaxy, we see the billions of distant stars in the spiral arms as the faint ring known as the Milky Way encircling the Earth.
Yet, if we scan the sky in the late evening at this Spring season, the Milky Way is nowhere to be seen. That's because the plane of our galaxy is tilted at a steep angle to the plane of the celestial equator, and we, at 40 degrees north latitude, are currently oriented so that the circular plane of the Milky Way is draped along the circle of our horizon and the sky-glow along the horizon from neighboring towns washes out the faint glow of the Milky Way. Since our horizon marks the plane of our galaxy, the galactic axis of rotation must lie directly overhead. At the zenith near midnight this week, we find the constellation Coma Berenices, or Berenice's Tresses. This group of rather faint stars includes a sparkling open cluster of stars, visible to the naked eye, but greatly enhanced with binoculars. At 250 light years, this is one of the closest star clusters, but since we are looking out perpendicular to our galactic plane, away from the obscuring dust clouds, we can peer far past this star cluster, deep into the farthest reaches of the cosmos. At 50 million light years, our line of sight encounters one of the most amazing sights in the night sky - a giant cluster of galaxies spilling down from the Big Dipper southward through Coma, toward Spica, the lovely blue-white, first magnitude star in the constellation Virgo, now well up in the southern sky. Our own local group of galaxies may be an outlying member of this giant group known as the Virgo Cluster. A modest telescope can pick out dozens of galaxies in this spectacular group which has been described as a broad band of softly glowing, phosphorescent jellyfish floating in the black ocean of the night sky.
This is the Skywatch Line for Monday and Tuesday, April 14th and 15th.
by Joe Slomka
The Sun sets at 7:33, with night falling at 9:19 PM. Dawn breaks at 4:30 AM and ends with sunrise at 6:13.
As the Sun sets, Mars lies high in the South. It appears as a dim, red object in the middle of the constellation Gemini. Mars marches across Gemini this month and will enter Cancer in May. The ten-day-old Moon lies between Mars and the pairing of the planet Saturn and the star Regulus. Tuesday night sees a fatter Moon beneath Leo's belly. The brightest star Sirius blazes well below Mars. Midnight sees the scene shift westward, with summer constellations rising behind Leo.
Before Dawn, the Milky Way, flowing from the North to South, accompanies the summer constellations. Jupiter escorts teapot-shaped Sagittarius in the South. Jupiter appears to the left of the teapot's handle. Binoculars reveal two Galilean moons to each side of Jupiter.
Astronomers, both amateur and professional, tend to observe objects or events that hold more appeal than others. Some only study the Moon, others planets, still others galaxies, or other specialties. Eclipses are the most available both astronomers and the general public. Outside of cautious observation of the Sun, the general public requires no special equipment. Amateur astronomers observe solar eclipses with safe telescopes and photographic equipment. Professionals observe eclipses to discover insights into the processes within the Sun. A 1922 solar eclipse verified Einstein's Theory of Relativity. A related event, "transits," occurs when a small body passes in front of a star. Transits of Mercury and Venus across the face of the Sun are rare and exciting to observe. Recently, several extra solar planets were discovered when they transited their suns and briefly dimmed the starlight.
The Albany Area Amateur Astronomers hold their monthly meeting on Tuesday, April 15 at 7:30 PM in the Schenectady Museum's auditorium. This month's guest speaker is Dr. Jay Pasachoff, Professor of Astronomy at Williams College; his topic will be eclipses and transits. Dr. Pasachoff is a world-renowned specialist in eclipses and transits, witnessing over 42 events.
On Friday night the Moon, approaching first quarter, will be very close to Mars. Look for the pair in the southwestern sky around 10:00 PM. Mars will be the bright reddish star above and slightly left of the Moon. By Saturday night the Moon, just past first quarter, will be above and to Mars' left, and not far from Castor and Pollux, the brightest stars in Gemini, the Twins.
Weather permitting the Albany Area Amateur Astronomers will hold a Star Party in Glenville's Indian Meadows Park beginning at 9:00 PM on Saturday, April 12. A variety of telescopes will be on hand to provide views of Saturn, the Moon, and other celestial wonders. The star party is canceled if the skies are mostly cloudy. If in doubt about the weather, or for further information, call 374-8460.
The International Space Station will be visible on Saturday night. It will appear brighter than the other stars in the sky as it glides among the stars. It will first be visible just after 8:19 PM coming up from the west northwestern horizon. It will be highest just after 8:22 when it will be 41 degrees above the southwestern horizon, and will vanish in the south southeast at 8:25. The path of the ISS will take it through Taurus, across the top of Orion, and below Sirius, the brightest star in the sky. As it passes below Sirius, see if the space station appears brighter than the star.
The Albany Area Amateur Astronomers will meet at 7:30 PM on Tuesday, April 15, in the auditorium at the Schenectady Museum. Jay Pasachoff, Director of Hopkins Observatory and Field Memorial Professor of Astronomy at Williams College, will be their guest speaker. His talk will be "Eclipses and Transits." Dr. Pasachoff is one of the world's experts on eclipses and a wonderful speaker. The meeting is open to all and there is no charge.
Skywatch line for Wed. and Thurs. April 9 and 10, 2008:
by Ray Bogucki
Observers last night (Tuesday), watching the crescent Moon occulting stars in the Pleiades, may have noticed that the Moon finally set well north of the west. This occurrence is explained by the Moon's location relative to the celestial equator. For any given location on the Earth's surface, the celestial equator, the projection of the Earth's equator on the celestial sphere, occupies a fixed position in the sky. From a position near Albany NY, at approximately 43 degrees north latitude, the celestial equator describes an arc that rises in the east at a 47 degree angle, climbs to a maximum 47 degrees above the southern horizon, and drops into the west, again at a 47 degree angle. Because of the 23 degree tilt of the Earth's rotational axis to its orbital plane, the Sun's path through the sky, known as the ecliptic, will be tilted 23 degrees to the plane of the celestial equator. Thus the ecliptic can reach up to 23 degrees north or south of the celestial equator. The Moon travels close to the ecliptic but can vary up to 5 degrees north or south of the ecliptic.
Tomorrow night (Thursday), the waxing crescent Moon will be at the northernmost point of the ecliptic and its own northernmost 5 degrees above the ecliptic. This will place it 75 degrees above the southern horizon. Look for the Moon after sunset. It will seem to be unusually high in the southern sky. Because the planets also stay close to the ecliptic, they may find themselves well north or south of the fixed celestial equator. Mars is currently at the northernmost, or highest, point of the ecliptic and is thus very high and well placed for observing. Mars has resumed its normal eastward motion and by the end of April will be passing close to Pollux in Gemini.
East of Mars and close to Regulus, bright Saturn is also well north of the celestial equator and is the dominant planet this Spring. Its rings show a tilt of about 10 degrees to our line of sight, and will gradually close down for the rest of the year. Jupiter, which rises near 2:30 a.m., is located about 22 degrees south of, or below, the celestial equator and so will remain quite low in the southern sky, where air turbulence near the horizon diminishes the quality of its telescopic image. Jupiter's orbital period is almost 12 years, so it spends roughly one year in each of the 12 Zodiac constellations it passes through. Thus, it will be a couple of years before it crosses to the north of the celestial equator and again provides the superior viewing it is famous for.
This is the Skywatch Line for Monday and Tuesday, April Seventh and Eighth.
by Joe Slomka
The Sun sets at 7:25 PM, with night falling at 9:08. Dawn breaks at 4:44 AM and ends with sunrise at 6:25.
On Monday's sunset, a two-day-old Moon forms a thin crescent in the southwest. Tuesday's three-day-old Moon lies closer to Mars. Mars appears high in the South; nightfall reveals its slow procession across the constellation Gemini. Saturn is the third object, high in the southeast. Saturn is closing in on Regulus, the brightest star in Leo.
Dawn finds Jupiter shining brightly to the east of teapot-shaped Sagittarius. Venus may be visible shortly before sunrise. The brilliant planet lies so close to the eastern horizon that any natural or atmospheric obstruction hides it. Venus will shortly disappear and become an "evening star" during July or August.
A nighttime observer sees that while the Moon rises in the East and sets in the West, it also proceeds eastward. In its travels, the Moon routinely occults, or eclipses, many stars. Tuesday night presents a dramatic example. At nightfall, the Moon begins eclipsing the Pleiades, a star cluster that resembles a "mini-dipper." The unlit side crosses northern stars and hides them. These stars emerge later from the thin lit crescent. This event continues while both the Pleiades and the Moon set about 11 PM. While naked eye observers can follow the action, those with binoculars will experience a detailed view of each star winking out and later reappearing.
The Pleiades, also known as M-45 and the Seven Sisters, are among the oldest known deep sky objects. Ancient Chinese observed the Pleiades during the vernal equinox of 2357 BC. Several books of the Bible mention the Pleiades. Ancient Greeks worshiped them. The word "Pleiades," may derive from the Greek verb "to sail," since the cluster rose when the sailing season began and set when it ended. The Seven Sisters were nymphs, daughters of Atlas and Pleione. Since most people see six stars, there is a legend of the "Lost Pleiad." Several stars are mentioned, but none can be definitively identified. The Pleiades are classified as an "open star cluster," about 367 light years distant.
Clear Skies
Joe Slomka
This is Dudley Observatory's Skywatch Line for Friday, April 4, through Sunday, April 6.
by Alan French
The Moon is new late Saturday night, so the weekend skies will be dark and moonless. Only a thin young crescent Moon will be visible in the early evening sky on Sunday night. On Sunday night the Sun will set at 8:28, and you will want to look for the slender Moon at 9:00 PM. It will be just five degrees above the west northwestern horizon, so you'll need a good clear view in that direction (remember that a fist held at arm's length spans 10 degrees across the knuckles). The “age” of the Moon you see will be 21 hours – meaning it is 21 hours past new.
The first two stars visible above the Moon as the sky darkens are in the constellation Aries, the Ram. The brightest and highest is Hamal, and the other is Sheratan. Hamal lies at a distance of 66 light years, while Sheratan lies slightly closer, at 60 light years. Sheratan is actually a double star, where the stars are too close together to be separated by a telescope. The duplicity was discovered by looking at the star's spectrum, which showed Doppler changes because the pair is close together and moving rapidly around each other.
Aries is known as the first sign of the Zodiac. Two thousand years ago the vernal equinox, marking the first day of spring and where the Sun's path crosses the celestial equator heading north, was in Aries. The Earth, however, wobbles like a top, with one “wobble” taking 26,000 years. The vernal equinox has moved westward in the past two thousand years, and is now in Pisces, the Fish. Since we are just past the vernal equinox, the Sun now resides in Pisces, so the constellation is in the daytime sky and not visible.
Saturn continues to be up most of the night, appearing in the south southeastern skies as the Sun sets. It is in the constellation Leo, the Lion, near Leo's brightest star, Regulus. Saturn is dues south and highest at 11:12 PM, and sets at 4:23 AM. Planets are best seen through a telescope when they are high in the sky, so the best views of Saturn will be between around 10:00 AM and midnight. Virtually any telescope magnifying thirty times or more will reveal the rings, and they are always a lovely sight.
Even binoculars will show Titan, the brightest Moon orbiting Saturn. On Saturday and Sunday nights Titan will be to the east or left of Saturn. A modest telescope will also easily reveal Rhea, which will be just east of the planet and slightly below the rings on Saturday, and between the planet and Titan on Sunday night. If you do a web search on “observing Saturn's moons” you should find some tools to show their locations at any time. Dione and Tethys are the next easiest moons to spot in a telescope.
Skywatch line for Wed. and Thurs., April 2 and 3, 2008:
by Ray Bogucki
This is the Skywatch Line for Monday and Tuesday, March 31st and April First.
by Joe Slomka
The Sun sets at 7:17 PM. Night falls at 8:58. Dawn breaks at 4:59 AM, ending with sunrise at 6:37.
As the Sun sets, Mars and Saturn continue to be the first planets visible. Mars lies due south at nightfall; Saturn is highest about 10:30 PM. Both planets are on the move; Mars slowly crosses Gemini this month, while Saturn creeps up to Regulus, in Leo. Mars sets before Dawn, while Saturn sets at first light.
Jupiter and the Moon are already up by Dawn's first light. Jupiter floats east of teapot-shaped Sagittarius. Early rising observers of Jupiter have to be alert. Jupiter lies within the Milky Way; it is possible to mistake a star for one of the Galilean moons. Magazines, almanacs or web sites help the observer.
A twenty-four day-old Moon resides in Capricornus. Neptune stands one degree above the Moon. Early observers can use the Moon as a guide to this distant member of our Solar System, despite the Moon's brilliance.
Already well up by Dawn, Antares is one of two giant stars that are easily visible. The other is Betelgeuse. Antares is the 15th brightest star in our sky. Both Antares and Betelgeuse are classified as “M” stars. “M” class stars, like Antares and Betelgeuse, have “left the main sequence,” which means that they no longer behave like normal stars and show signs of old age. Stars of this kind are usually bloated; Antares is about 600 million miles in diameter. These stars are also slightly variable in their light output, and show signs of pulsing.
Nightfall finds Canis Major, the Big Dog, almost due South. A chain of stars reaches up from the horizon to the dog's hindquarters. This is the constellation Puppis. Puppis represents part of the obsolete large constellation, Argo Navis. Jason and his crew, the Argonauts, manned the legendary vessel. For centuries, the ship was a whole constellation. In 1879, astronomers broke it into parts: Puppis (Poopdeck), Carina (Keel), Pyxis (Compass) and Vela (Sails).
|
|
|
|
Dudley Observatory |
|
|
Copyright © 2007 Dudley Observatory. All Rights Reserved. |
|