Making New Mirrors

Proof of Concept for Silica Mirror (Thomson Papers, B#6, F001)

Proof of Concept for Silica Mirror, 36″ (Thomson Papers, B#6, F001)

This doesn’t look like much, but it was the start of something that was going to revolutionize the field of astronomy.  This is a disk of silicon dioxide, also known as silica.  Since it is made from very clean quartz sand, it is also known as “fused quartz”.  You can think of silica as being very pure glass without any additives.

Those additives serve a purpose.  They lower the melting temperature of the silica.  Without those, silica can require a furnace at 3,000 degrees Fahrenheit to work with.  But removing those additives means that you have a type of glass that is very resistant to changes in temperature.

One of the first people to see the advantages in this was Elihu Thomson, a scientist, engineer and businessman who founded the Thomson-Houston Electric Company.  This company later merged with Edison General Electric to create the General Electric company we’re familiar with today.

Since fused quartz is so resistant to heat, it has been used in high temperature applications like halogen lamps and furnaces.  It’s strong, so it has been used in bathyspheres and other high-pressure devices.  But Thomson was an avid amateur astronomer, and he saw a use for silica that others might have missed: telescope mirrors.

Since silica resists changing shape with heat, it could be used in unheated observatories that could get blistering hot or freezing cold without distorting the viewing.  It could also resist the heat produced by grinding and polishing, which made it easier and faster to work with that regular glass.  Mirrors could be produced faster and – more importantly – larger than ever before.

In the late 1920s, when George Hale convinced the Carnegie Institution to fund the construction of a new telescope for the Palomar Observatory, he was thinking big.  Hale had already worked on the largest telescope in the world: the 40-inch refracting telescope at Yerkes Observatory, 60-inch Hale reflecting telescope at Mount Wilson Observatory and 100-inch Hooker reflecting telescope at Mount Wilson.  For his next – and final – telescope, he would require a massive 200 inch mirror.

This was probably beyond the conventional technology of the time.  Hale needed to try something new.  He ended up turning to Elihu Thomson and his idea for a fused silica mirror.

The lump at the upper right was a proof of concept.  The next mirror would be a sixty inch disk, and no one had worked with silica on that scale before.  It required new techniques and the construction of new furnaces in Thomson’s Lynn, Massachusetts plant.

Construction of a experimental furnace for the 60-inch Palomar Mirror (Thomson Papers, B#6, F006a)

Construction of a experimental furnace for the 60-inch Palomar Mirror (Thomson Papers, B#6, F006a)

In the end, it took three years to produce two sixty-inch mirror.  The first mirror was of excellent quality, but it cracked during the cooling process.  The second mirror was marred by air bubbles.  Thomson and  General Electric had proven that large scale silica mirrors could be made, but that wasn’t enough.  Hale needed something produce quickly, and at a reliable price.

So the 200-inch mirror was not made in a Schenectady factory, but in Corning Glass works.  And instead of silica, it was made of Pyrex.  One of the first attempts at the 200-inch mirror is on display at the Corning Museum of Glass.

It’s a little frustrating, but it’s a good example of the difference between a new technology and a more mature technology.  Pyrex had been invented in the 1890s, about the same time that Thomson began experimenting with fused quartz.  But Thomson was a businessman, and a busy one.  There was no immediate need for silica mirrors, and the potential market seemed small.  General Electric had plenty of other things to do.

Corning invested more time and energy into Pyrex, and so they went into the process with more confidence.  They succeeded in six months when GE it had taken three years to not quite pull it off.


Skywatch Line for Wednesday, September 14th and Thursday, September 15th 2016

This is the Dudley Observatory Skywatch Line for Wednesday, September 14th and Thursday, September 15th written by Louis Suarato.

The 95% illuminated, waxing gibbous Moon rises at 5:57 p.m. in the constellation Aquarius Wednesday. As the sky darkens, you’ll be able to locate the globular cluster, M2, about ten degrees above the Moon. Discovered in 1746 by Jean-Dominique Maraldi, M2, at 175 light-years in diameter, is one of the largest known globular clusters, and contains 150,000 stars. M2 is 37,500 light-years from Earth, and is estimated to be about 13 billion years old, making it one of the oldest globular clusters in the Milky Way Galaxy. M2 can be seen with the naked eye under optimal conditions, but better viewed through binoculars or a small telescope. Larger telescopes will resolve individual stars within this cluster.

Mars and Saturn are now separated by 13 degrees, and can be found over the south-southeastern horizon between the constellations Scorpius and Ophiuchus. If you look 20 degrees above Saturn, you’ll find globular cluster M10 in Ophiuchus. Look four degrees to the right of M10 for globular cluster M12. Both globular clusters were discovered by Charles Messier in 1764, M10 on May 29th, and M12 on May 30th. Ophiuchus is also the home of the Summer Beehive open star cluster. Look about 15 degrees above M10 for this open cluster. The Summer Beehive, or IC 4665, is a large cluster that can be viewed through binoculars.

The nearly Full Moon rises at 6:34 p.m., Thursday, a half hour before sunset. Use the Moon on this night to find Neptune. Look for Neptune 2 degrees to the right of the Moon. At an average distance of 30.1 astronomical units, Neptune is the eighth, and farthest known planet from the Sun. One astronomical unit is equal to 93 million miles. Neptune is not visible to the naked eye, so, use binoculars or a telescope to view this planet.

The Albany Area Amateur Astronomers invite you to join them for their monthly meeting this Thursday beginning at 7:30 at miSci in Schenectady. This month’s speaker is Albany Physicist Dr. Vivek Jain. Dr. Jain is part of the team that manages the ATLAS instrument, one of two general-purpose detectors at CERN, the European Organization for Nuclear Research. Dr. Jain will be discussing the link between particle physics and Cosmology. The directions to miSci can be found at

Skywatch Line for Friday, May 6, through Sunday, May 8, 2016

This is Dudley Observatory’s Skywatch Line for Friday, May 6, through Sunday, May 8, written by Sam Salem.

On Friday, the Sun rises at 5:43am and sets at 8:02pm. The New Moon occurs at 3:30pm, this afternoon, and sets a few minutes before sunset, around 7:58pm. On Saturday, the New Moon sets at 9:10pm, try to catch the hairline crescent Moon twenty or thirty minutes after sunset, just a few degrees above the west-northwest horizon, Aldebaran is a few degrees above or upper left. Binoculars will help finding the 28 hours young Moon.

Jupiter reaches its transit altitude around 8:55pm on Friday and sets around 3:30am the next day. Tonight is the last chance to see a double shadow transit on Jupiter this apparition. Watch the two shadows on Jupiter as both Callisto and Io cast their tiny black shadows onto Jupiter’s sunlit face from 12:38 to 1:42 am tonight. Io’s shadow joins Callisto’s on the Jovian disk around 12:38am. Callisto’s shadow leaves the planet around 1:42am.

On Friday, Mars rises around 9:36pm, reaches its transit altitude around 2:17am and sets shortly after sunrise. Mars is entering its closest two-month charm in a decade. Blazing upper in constellation Scorpius, as it climbs higher, you’ll find Antares below it and Saturn to its lower left. Mars continues to grow in diameter as Earth continues to approach it. Mars will come to opposition on the night of May 21–22. For several days around its closest approach to Earth on May 30th, it will reach its largest since 2005.

The return of bright globular clusters to the evening sky is a signal that summer is just around the corner. This moonless weekend provides a good opportunity to search out for one of the globular star clusters that has gone on to become one of the best-studied objects in the night sky. Messier Object 3 (M3 or NGC 5272) is considered by amateur astronomers to be one of the finest clusters. As darkness arrives, M3 is in prime position nearly overhead. M3 is located in the northern starless space of constellation of Canes Venatici on the border with Boötes. The easiest way to pin down M3 is to draw an imaginary line connecting the stars Arcturus and Cor Corali. M3 is situated a little less than half way from Arcturus. The cluster is an easy catch in binoculars, which show it as a slightly bloated, fuzzy “star.” With a small telescopes used at moderate magnification you will start to resolve individual cluster members, and the view in an 8- or 10-inch scope can be spectacular. In 1764, Charles Messier logged M3 as a “Nebula without star”. With his small telescope, rather like the finder scope of a modern amateur telescope, Messier could not resolve M3 into stars.

Mercury will make its daytime transit across the Sun’s face on Monday. You can join the Dudley Observatory at miSci for this special event on Monday from 9am—3pm. See the link below. Special telescopes will be set up for safe solar viewing, hands-on sun-themed activities throughout the gallery, and a live stream of the transit. The entire transit is visible in Eastern North America. Don’t miss it as the next transit of Mercury won’t occur until 2019.

Skywatch Line for Monday and Tuesday, May 2 and 3, 2016

This is the Dudley Observatory Skywatch Line for Monday and Tuesday, May second and third written by Joe Slomka.

The Sun sets at 7:57 PM; night falls at 9:49. Dawn breaks at 3:54 AM and ends with the Sun rising at 5:46.

By civil twilight, only one planet, Jupiter is easily seen, at minus 2.2 magnitude. Jupiter has already risen by sunset; it is best observed at about 9:10 PM. Days are growing longer, so opportunities for spotting shadows on Jupiter are growing slim. However, the Great Red Spot, a giant storm on Jupiter, is visible to telescopic observers at 2:09 AM, Wednesday. Jupiter sets at 3:42 AM.

Mercury is also in the western twilight sky. However, it is quite low, about three degrees high, and dim, only third magnitude. This poses a challenge for the observer, who needs an unobstructed horizon to even try for success. Mercury sets at about 8:52 PM, and is preparing for its Monday, May 9thtransit across the Sun. The Dudley Observatory and miSci will have telescopes and other instruments that provide safe ways to view the Sun and Mercury.

Mars, Saturn and the star Antares make their appearance at Midnight. Mars rises first, at 9:50 PM in Scorpius. Mars is also preparing for its own special event – its opposition. Every two years, Mars approaches Earth. This time it is the best in eleven years. As May begins, it is retrograding, moving westward. During the month, it steadily becomes brighter, and larger in our instruments. Binocular and telescopic sky watchers are beginning to see details on the Martian surface. The Albany Area Astronomers will host star parties, weather permitting, this month. The public is invited to see Mars up close. Mars is best seen at about 2:30 AM and sets during daytime.

Saturn, in Ophiuchus, follows Mars a half-hour later early in the month; later, due to Mars’ retrograde motion, it lags to an hour behind. Saturn, also, is becoming brighter and larger in our eyepieces. It will have its own opposition in early June. The Saturnian rings are tipped almost to maximum for our enjoyment. Depending on telescope size, several of Saturn’s 62 moons are visible. Astronomy magazines, websites and apps assist the viewer in identifying them.

Saturn, Mars and Scorpius’ brightest star, Antares, fly in a triangular pattern all month. However, again due to Mars’ rapid westward motion, the gap between Mars and Saturn increases.

Neptune rises in Aquarius during Astronomical Dawn. It lies low on the eastern horizon, appears at about eighth magnitude, and disappears as the sky brightens.

The Moon rises at 3:59 AM Tuesday, it emerges in Pisces and blazes at minus seventh magnitude. It looks about 16 percent illuminated. Wednesday, it rises in Cetus at 4:35 AM, shining at minus 5.1 magnitude and only 9 percent illuminated. Wednesday finds the Moon only six degrees above the eastern horizon. This is the last easily seen Old Moon of this lunar month.

Skywatch Line for Friday, April 22, through Sunday, April 24, 2016

This is Dudley Observatory’s Skywatch Line for Friday, April 22, through Sunday, April 24, written by Sam Salem.

On Friday, the Sun rises at 6:02am and sets at 7:47pm. The full Moon occurs at 1:24am on Friday. The full Moon that appears in April is called the Pink Moon. This name came from the herb moss pink, or wild ground phlox, which is one of the early spring flowers. It is also known as the Sprouting Grass Moon, the Egg Moon, and the Fish Moon. Early Colonial Americans used these names as they learned them from the local Native Americans. These names usually describe some activity done by those tribes during that time in their location as they used to track the time by observing the seasons and lunar months.

The Moon rises at 8:17pm on Friday, 9:13pm on Saturday, 10:09pm on Sunday.

Full Moon is out all night at the peak of this year’s Lyrid meteor shower. The annual Lyrid meteor shower is active each year from about April 16 to 25. This year the peak of this shower, which tends to come in a burst and usually last for less than a day, is expected to fall on the morning of April 22nd under the glaring light of the full Moon.

Mercury remains well-placed low in the west-northwest in twilight, but it’s fading fast.

On Sunday, around midnight watch Saturn and the red supergiant star Antares follow the waning gibbous Moon and Mars over the southeast horizon

Look high in the West for Pollux and Castor lined up early at night. The heads of the Gemini twins, Pollux and Castor, form the top of the Arch of Spring. The two ends of the Arch are Procyon to their lower left, and brighter Capella farther to their lower right.

Arcturus is the brightest star in the east. Spica shines to its lower right. To the right of Spica is the four-star constellation Corvus, the Crow of Spring. It is recognizable for its compact, boxy shape. In Greek mythology, Corvus was seen as the cupbearer to Apollo, god of the Sun.

Friday is the Earth Day. It is an annual event celebrated on April 22, on which day events worldwide are held to demonstrate support for environmental protection. It was first celebrated in 1970. While the Earth Day was first focused on the United States, it is now coordinated globally and celebrated by more than 193 countries each year. There are many ways to celebrate the Earth Day. You could plant a tree, make a meal with locally grown vegetables, clean up trash in the neighborhood, or save power.

Skywatch Line for Wednesday, April 20th and Thursday, April 21st, 2016

This is the Dudley Observatory Skywatch Line for Wednesday, April 20th and Thursday, April 21st written by Louis Suarato

The 99% illuminated, waxing gibbous Moon rises at 6:22 p.m. Wednesday. The Full Moon occurs at 1:24 a.m. Friday. April’s Full Moon was known as the Full Pink Moon by some northeastern Native American tribes. The reason being it’s the time for seeing moss pink, or wild ground phlox, one of Spring’s first flowers. The Farmer’s Almanac tells us that this month’s Full Moon is also known as the Sprouting Grass Moon, the Egg Moon, and the Fish Moon. The Moon reaches apogee, its furthest distance from Earth during this lunar month, at 12:05 p.m. Thursday, 252,495 miles away. You can locate Virgo’s brightest star, Spica, 5 degrees below the Moon at 11 p.m. Wednesday. The Moon and star will move a degree closer through the night.

At sunset Wednesday, and Thursday, with the nearly Full Moon rising, Jupiter will appear approximately 50 degrees over the southeastern horizon. Mercury will be setting in the west at that time, about 14 degrees over the west-southwestern horizon. Look for the Pleiades star cluster about 8 degrees above Mercury. You’ll find the Beehive Cluster, or M44, to the west, between Jupiter and the heads of Gemini, Castor and Pollux. Mars rises in the constellation Scorpius at 10:50 p.m., followed by Saturn about a half hour later. The two planets are now separated by 8 degrees. Scorpius’ brightest star, Antares, and the globular cluster, M4, can be found 5 degrees below Mars, and can best be seen in the pre-dawn sky when the two planets, the red super-giant star, and globular star cluster are 20 to 24 degrees above the southern horizon.

If you would like the opportunity to meet other people interested in astronomy, the Albany Area Amateur Astronomers will be holding their monthly meeting at miSci, in Schenectady, beginning at 7:30 p.m. Thursday. These meetings usually include a discussion of current astronomical events and/or answers to questions about telescopic equipment. Non-members are always welcome.

Skywatch Line for Monday and Tuesday, April 18 and 19, 2016

This is the Skywatch Line for Monday and Tuesday, April 18th and 19th.

The Sun sets at 7:41 PM; night falls at 9:26. Dawn breaks at 4:22 AM and ends with sunrise at 6:06.

The twelve-day-old Moon blazes at minus 11 Monday night and is best observed at 10:50. Tuesday night finds a brighter and fuller Moon highest at 11:32. It occupies Virgo both nights and sets after 5 AM both days.

Jupiter is also already up. It is located under Leo’s belly and is best seen at about 10 PM. While binocular watchers can see Jupiter and some of its four Galilean moons. Telescope users can witness events on Jupiter. Wednesday at 12:16 AM, one can see the Great Red Spot, a giant storm, on Jupiter’s face. Telescopes also reveal the moon Callisto begin its march across Jupiter at 8:38 PM Tuesday and exit the planet’s surface at 11:37 PM. Jupiter sets after 4:30 AM.

Mercury makes the best appearance of the year on Monday. It appears about 19 degrees above the western horizon. It shines is about 0.2 magnitude and, in telescopes, appears about 8 arc seconds in size. Mercury is at greatest elongation tonight, about twenty degrees east of the Moon. Use binoculars to spot it amid the sunset sky. Mercury sets about 9:30 PM.

Mars rises in Ophiuchus at 10:51 PM. The Red Planet steadily grows brighter and larger in our telescopes in preparation for its May opposition. Saturn, also in Ophiuchus, rises about a half-hour after Mars. Mars shines at minus 1.1 magnitude, while Saturn is a sedate zero magnitude. Both are best observed at about 4 AM. Saturn, Mars and the bright star Antares form a neat triangle Tuesday morning. Mars is the triangle’s apex, with Saturn seven degrees to Mars’ East and Antares about five degrees below Mars. All three are great sights in any size telescope. Saturn is famous for its rings, Mars for its red color, and Antares for its rival color to Mars. All three remain up the rest of the night.

Besides the rings, Saturn has sixty-two moons. One of these, Iapetus, has puzzled observers for centuries. Iapetus is bright when it is on one side of Saturn, but markedly darker when on the other.

Two groups of astronomers think they have figured it out. Iapetus is tidally locked to Saturn, just like the Earth’s Moon – showing the same side to the planet. The leading side of Iapetus sweeps up debris from a newly discovered (and invisible to amateurs) ring. Thus one side looks like it was covered in chocolate dust, while the trailing side is as white as snow, really ice. In addition, the dust, warmed by sunlight, melts the ice below, which flows to the trailing side and re-freezes. Iapetus has a 79.3-day orbit, and is visible in amateur telescopes. Astronomy programs and websites assist the observer.

The Albany Area Amateur Astronomers hold their monthly meeting at miSci on Thursday, April 21st at 7:30 PM. This month, club member David Scott talks about the Analemma, that strange figure-eight you see on maps and globes. He will explain it and how it helps astronomers. All club events are free and open to the public.

Dudley Observatory Skywatch Line for Friday, April 15, through Sunday, April 17, 2016

This is Dudley Observatory’s Skywatch Line for Friday, April 15, through Sunday, April 17, written by Sam Salem.

On Friday, the Sun rises at 6:15am and sets at 7:39pm. Look for the waxing gibbous Moon with 65% of its visible disk illuminated on Friday, increasing to 74% on Saturday, and 82% on Sunday night. The Moon sets at 2:58 am on Friday, 3:34 am on Saturday, 4:06 am on Sunday, and 4:36 am on Monday.

On Friday evening, the Moon forms a curving row with Regulus to its left and then Jupiter.  Look above the Moon after dusk, on Saturday, for Regulus, the bottom of the now-vertical Sickle of Leo.  Regulus is the brightest star in the constellation Leo.  On Sunday, watch as the Moon pays a visit to the brightest planet of the night, Jupiter, as both rise in the southern sky.

Mars begins its retrograde motion westward in the sky, on Sunday.  Mars will continue its backward march until June 30.  For a couple of months every two years, Mars changes the direction of its motion against the backdrop of fixed stars. This apparent reversal is due to the fact that Earth is orbiting closer to the sun than Mars and is moving faster on its orbital track. That means our planet periodically passes Mars, creating the illusion that it has changed course. Seen from Mars, Earth appears to be in retrograde during this time.

Mid-April Mars is 63,236,776 miles away from Earth.  Now is the time to start exploring Mars through the telescope.  It blazes highest in the south before the first light of dawn, to the right of dimmer Saturn and above Antares.  In a telescope Mars grows this week from 13 to 14 arc-seconds in diameter.   By the time of its opposition and closest approach in late May, Mars will triple in brightness and grow to 18.8 arc-seconds wide.

Saturn is also moving retrograde but at much slower speed than Mars.  The pair moves apart from each other then start to converge and pass each other on August 25.

By early dawn, Saturn and Mars stand in the south-southwest.  Saturn, Mars, and Antares form a triangle.  Saturn stands on the left, Mars stands on the right, and the fainter, Mars-colored Antares stands beneath Mars.  Antares is the brightest star in the constellation Scorpius.  It is often referred to as “the heart of the scorpion”.  Along with Aldebaran, Regulus, and Fomalhut, Antares comprises the group known as the “Royal Stars of Persia”.   They were regarded as the guardians of the sky during the time of the Ancient Persians.  Persians believed that the sky was divided into four districts with each district being guarded by one of the four Royal Stars.

Skywatch Line for Monday and Tuesday, April 11th and 12th, 2016

This is the Skywatch Line for Monday and Tuesday, April 11th and 12th

The Sun sets at 7:33 PM; night falls at 9:15. Dawn breaks at 4:37 AM and ends with the Sun rising at 6:18.

The Moon dominates the sky on both nights. Monday, the five-day-old Moon blazes at minus 8.3 magnitude in Taurus; Tuesday finds it in Gemini shining brighter at magnitude minus 9.1. It sets after midnight on both nights.

Jupiter still resides in Leo; it rises about 4 PM and lies under Leo’s belly. Jupiter is best seen at about 10:37 PM. While the binocular observer can see the planet and some of its moons, a telescopic astronomer can make out the weather bands, witness the Jovian moon Io disappear behind the giant planet at 2:26 AM, Wednesday and see the Great Red Spot (a giant storm on Jupiter) at 11:49 PM Tuesday.

The twilight sky also hosts Mercury. As mentioned last week, this is Mercury’s best appearance of the year. It hovers at about eleven degrees above the western horizon and shines at magnitude minus 0.6. It sets at about 9:11 PM. There are no brighter stars in Mercury’s neighborhood, so identification should be easier. In a telescope it appears about 62 percent illuminated.

Mars rises in Ophiuchus at about 11:15 PM and is best observed at approximately 4 AM. Mars continues to brighten and grow larger in our telescopes in preparation for its May opposition. Saturn, also in Ophiuchus, rises a half hour after Mars. Saturn shines at a sedate 0.3 magnitude. Compare Mars’ color with that of the star Antares in nearby Scorpius. Also note the distance between Saturn and Mars; they come closer to each other until April 17th.

Jupiter, Mars and Saturn remain up the rest of the night.

Jupiter points to another constellation to Leo’s right – Hydra. Hydra begins with a diamond-shaped head and the rest of the body extends southward. In fact, Hydra is the longest and largest constellation. One must travel well South to enjoy Hydra to its fullest extent. Hydra is unique in that two smaller constellations ride atop it: Crater, the Cup, and Corvus, the Crow. In Greek mythology, Hydra is a mythical water snake. It attacked Jason and his shipmates on the good ship Argo. In Roman myths, Corvus was commanded by Apollo to bring a cup of water, but got sidetracked by ripening grapes. Corvus tried to excuse his tardiness by blaming the snake. Do not confuse Hydra with the similar sounding constellation Hydrus. Hydrus is relatively modern. It was one of many, invented by explorers who ventured below the equator for the first time.

Skywatch Line for Friday, April 8, through Sunday, April 10, 2016

This is Dudley Observatory’s Skywatch Line for Friday, April 8, through Sunday, April 10, written by Sam Salem.

This is a weekend amateur astronomers throughout the Northeast look forward to the annual Northeast Astronomy Forum (NEAF) at SUNY Rockland Community College in Suffern, New York. This is the world’s largest trade show of telescopes and accessories, and it’s only a two to three hour drive from the Capital District region. In addition to exhibits by more than 100 vendors, there are lectures, programs for beginners, and special events for children. Weather permitting; there is also solar party daily observing, where some of the finest safe solar telescopes provide fantastic views of the Sun, in white light and the red light of glowing hydrogen.  Event hours are 8:30 am to 6:00 pm, Saturday, April 9, and 10:30 am to 5:00 pm, Sunday, April 10. For full details visit the NEAF website.

On Friday, the Sun rises at 6:25am and sets at 7:31pm. The New Moon occurred on Thursday, at 7:24am. Waxing crescent of the Moon’s visible disk is 2% illuminated on Friday, increasing to 7% illumination on Saturday, and 15% on Sunday night.  The Moon sets at 9:11pm Friday, 10:24pm Saturday, and 11:32pm Sunday.

On Saturday, the crescent Moon shines in the west in twilight.  Look for Mercury far down to its lower right.  Mercury just passed the perihelion point of its orbit, when it’s closest to the sun. Therefore, it is moving rapidly, becoming more favorably placed with each passing day.

As the stars come out, spot Aldebaran to the Moon’s upper left and the Pleiades to its upper right.  Aldebaran is a giant star.  It is the brightest star in the zodiac constellation of Taurus.  The name Aldebaran means “the follower” in Arabic.  Presumably, it got this name because it rises near and soon after the Pleiades.  Aldebaran is about 65 light years away.  The planetary exploration probe Pioneer 10 is currently heading in the general direction of Aldebaran and should make its closest approach in about two million years.

Venus is deep in the glow of sunrise.  Saturn and Mars continue to move closer to each other until April 20 when the minimum distance between them is reached. Saturn shines near Mars from late evening until dawn where they are both near Antares in the constellation Scorpius.

Jupiter continues to be the brightest planet on April nights.  It is the only planet to light up the sky almost immediately after sunset.  The giant plant climbs highest up to its transit altitude around 10:50pm and sets in the west before dawn.  Although Jupiter is almost impossible to miss, it might be possible to confuse it with Sirius, the brightest star in the night sky.  At nightfall and early evening, Jupiter moves over the eastern half of sky, while Sirius shines to the west of Jupiter, dominating over the western half of sky.  To confirm if you’re looking at Sirius, and not Jupiter, use the three stars forming the Orion’s belt to point down towards it.