First Night Out Series: Measuring Brightness In The Sky

In 120 B.C. Hipparchus, a Greek astronomer, ranked the brightness of stars in the sky on a scale of one to six. He classified the brightest stars he could see as first magnitude and ranked the rest down to the faintest at sixth magnitude.

Astronomers still use this scale to measure the brightness of celestial objects, although it has since been modernized.

The Magnitude Scale

The magnitude scale is logarithmic, so a difference of one point in magnitude is equal to a difference in brightness of about 2.5 times.

The magnitude of stars in the Big Dipper and Little Dipper asterisms.  Credit: Starry Night software.

A magnitude-one star is about 2.5 time brighter than a magnitude-two star, and a hundred times brighter than a magnitude-five star.

The lower the magnitude, the brighter the object.

The brighter planets and stars have negative magnitudes. The sun, the brightest object in the sky, has a magnitude of -26, followed by a full moon at magnitude -12.6.

Objects with a magnitude of six or less can be seen without optical aid under ideal observing conditions away from all artificial light.

Where Do Objects Fit in the Scale?

The table below is a list of well-known celestial objects and roughly where they fall on the magnitude scale—some objects, such as Venus, vary in brightness. The magnitude values have been rounded.

Object Mag
   
Sun -26
Full Moon -12.6
Crescent Moon -6
Venus (the brightest planet) -4
Jupiter -2
Sirius (the brightest star in the sky) -1
Vega (the brightest star in the Summer Triangle) 0
Saturn +1
Polaris (the North Star) and the Stars of the Big Dipper +2
The Andromeda Galaxy +4
Uranus and the Faintest Stars Visible with the Naked Eye +6
Objects You Need Binoculars to See +7 and greater

A Few Handy Terms

Here are a few handy terms to keep in mind when reading about the appearance of celestial objects.

Luminosity

Luminosity is the intrinsic brightness of a star—compared to the sun—as it would appear if you were there in orbit around it, rather than viewing it from Earth. The sun's luminosity is 1. Sirius has a luminosity of 23 and Betelgeuse has a luminosity of 55,000.

Brightness

Brightness is the light given off by a celestial object as seen from Earth. Brightness depends on luminosity and the distance from the object. 

Magnitude

Magnitude is a logarithmic brightness scale. Magnitude-one objects are 2.512 times brighter than magnitude-two objects, which are 2.512 times brighter than magnitude-three objects, and so on. The difference between magnitude one and magnitude five is one hundred times. The higher the magnitude, the fainter the object. The lower the magnitude, the brighter the object. The brightest stars have negative magnitudes.

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First Night Out Series: Measuring Distances In The Sky

Measuring the distance from one star to another in the sky is easy when you master using your hands to measure the degrees between objects. 

Hold your hand at arm's length:

  • The width of your little finger is about one degree—enough to cover the moon and sun, both of which are each half a degree across.
  • The width of the first three fingers side-by-side spans about five degrees.
  • A closed fist is about ten degrees.
  • If you spread out your fingers, the distance from the tip of your first finger to the tip of your little finger is 15 degrees.
  • If you spread out your fingers, the distance from little finger to thumb covers about 25 degrees of sky.

Measuring degrees with your hands.

With a bit of practice, this hand system is endlessly useful when measuring your way around the sky.

Calibrating with the Big Dipper

Everyone's hands are slightly different, so you might want to practice and calibrate your own hand measurements using the Big Dipper.

Big Dipper Distances.

Here are the rough distances from Dubhe to several other prominent Big Dipper stars:

Dubhe to Merak 5 degrees
Dubhe to Megrez 10 degrees
Dubhe to Alioth 15 degrees
Dubhe to Mizar 20 degrees
Dubhe to Alkaid 25 degrees

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Observing Saturn

On Friday, May 22, at 10 p.m. EDT, Saturn will be in opposition to the sun. This means that it will be directly opposite the sun in our sky. It will rise as the sun sets in the evening, shine brightly all night long, and set as the sun rises at dawn.

On May 22, Saturn reaches opposition with the Sun. It will be right on the border between Libra and Scorpius, just above the three stars which form the Scorpion’s claws. Credit: Starry Night software.

If you just look at the sky on a single night, everything seems quite static. But if you watch Saturn over a period of a few weeks and note its position against the background stars, you will see that it is in constant motion.

Currently Saturn is moving with what is called “retrograde motion,” from left to right against the background stars. This is actually an optical illusion caused by the Earth’s much more rapid movement around the sun. Once the Earth is well past Saturn in early August, Saturn will appear to reverse directions and begin moving in its true direction, from right to left.

This retrograde motion puzzled early skywatchers, who though the planets must go around it tiny circles called epicycles. This was because they incorrectly believed that the Earth was fixed in space and everything revolved around it, the “geocentric theory.” Once Copernicus made clear that the sun, not the Earth, was the center of the Solar System, the geometry of the planets’ motion became much simpler.

Saturn, like all the planets, is much smaller in angular size than most people realize. I once tried an experiment to see how much magnification was needed to see Saturn’s rings. With a binocular magnifying 10 times, Saturn looked just like a bright star. With a 15x binocular, I could just see a hint that Saturn was oval rather than round. It took a telescope magnifying 25 times to see Saturn’s true shape, though even then no detail was visible. I generally use magnifications of 150 to 250 times to see the details of Saturn and its ring system.

Saturn really has multiple rings, of which the brightest are the outer A ring and the inner B ring. The A ring is noticeably darker than the B ring, and the two are separated by the dark Cassini Division, named after 17th century Italian astronomer Giovanni Domenico Cassini, who was the first to observe it in 1675. Cassini also discovered four of Saturn’s five brightest moons.

The Cassini Division separates the A and B rings.

Titan, the largest and brightest of Saturn’s moons was discovered in 1655 by Dutch astronomer Christiaan Huygens. It is visible in even the smallest telescopes. It is the second largest moon in the Solar System (after Jupiter's moon Ganymede), the only moon to have a dense atmosphere, and the only moon other than our own to have been landed on by a spacecraft.

Huygens was also the first person to deduce that Saturn’s rings were flat circular objects in the plane of Saturn’s equator. Further study has shown that they are made up of thousands of tiny fragments of rock and ice. I once watched a star pass behind these rings, and the star continued to be visible, since there is more empty space that rock and ice in the rings, making them translucent.

Saturn’s smaller moons are worth looking for if you have a good telescope. The brighter ones are visible in a 90mm telescope. Because they are in constant motion around Saturn, you need a planetarium program like Starry Night to identify which ones are visible on a given night. Most of the bright moons move in the same plane as the rings, so appear to trace ovals around the planet.

In a telescope at about 150 power, Saturn is small but beautiful in its perfection, the jewel of the Solar System. Look around the planet for its brightest moons. Credit: Starry Night software.

Iapetus is a particularly interesting moon. Its orbit lies outside those of the other bright moons, and is tilted at an angle of 15 degrees compared to the other moons and the rings. Like all major moons in the Solar System, Iapetus always keeps one face permanently turned towards its planet. The side of Iapetus which leads it around in its orbit has encountered a large amount of debris, painting that face of the moon dark black. When that blackened side of Iapetus is facing Earth, at the moon’s greatest elongation east, it is almost two magnitudes fainter than when the trailing side of Iapetus is facing us, at greatest western elongation.

Right now Iapetus is close to its western elongation, so is at its brightest, magnitude 10.1. By greatest elongation east on June 27, it will be at its faintest, magnitude 11.9.

The globe of Saturn itself is rather bland when compared to its more active neighbor Jupiter. It shows a system of darker belts and brighter zones, but their contrast is muted compared to Jupiter. From time to time bright spots have been observed in Saturn’s cloud tops, but they have short lives compared to cloud features on Jupiter. In large telescopes, the polar regions of Saturn take on an olive green color.

It is interesting to observe the pattern of shadows on Saturn. The rings cast shadows on the globe of the planet, and the planet in turn casts its shadow on the rings. I have observed these shadows in a telescope as small as 90mm aperture under steady seeing conditions.

Whenever I observe Saturn in a telescope, I always take a few minutes to just sit back and admire its sheer beauty. Saturn was one of the first objects I looked at when I got my first telescope as a teenager, and I still recall the wonder I felt at witnessing this beauty for the first time with my own eyes: “It really has rings!”

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

First Night Out Series: Finding Your Way Around The Sky

The Big Dipper is a great starting point for learning the night sky. Being circumpolar, it never completely sets or dips below the horizon—it's visible in the night sky year-round!

The Big Dipper itself is not a constellation, but it resides in one called Ursa Major, the Great Bear, the third largest of the 88 constellations. The name originates from the dipper-shaped pattern formed by the seven main stars in the constellation.

To locate the Big Dipper, face north and look for the seven bright stars that dominate the sky in this direction—they should be easy to find. Depending on the time of year, the pattern formed by these stars appears in a difference orientation, but the shape is always the same:

  • In autumn, the dipper appears to be sitting flat.
  • In spring, the dipper is upside-down, spilling its contents.
  • In summer, it sits upright on its bowl.
  • In winter, it sits up on its handle.
The Big Dipper through the seasons.

The Big Dipper through the seasons.

The stars of the Big Dipper are a handy guide to other stars, constellations, and other thought-provoking objects that may be too faint to spot with the naked eye. Using well-known spots in the sky to find fainter ones is known as star hopping—think of it as an astronomical treasure hunt! And one of the easiest and coolest place to start is with the two end stars that form the front of the dipper's bowl—they point straight to Polaris, the North Star.

All the other stars in the sky seem to turn counterclockwise around Polaris. Polaris itself marks the end of the handle of another pattern, the Little Dipper in Ursa Minor, the Little Bear. If you find Polaris, you know which way is north. 

Following the arc of the handle of the Big Dipper points to two of spring's brightest stars—Arcturus and Spica. With a bit of practice, it's surprisingly easy to imagine lines and arcs from star to star and hop from constellations you know to those you're still learning.

The Big Dipper points the way.

The trick to successfully learning the night sky is to use easily recognizable star patterns to find the more difficult ones—just like we used the Big Dipper's stars to find Polaris.

Don't try to learn the entire sky on your first night out. Begin by learning the major constellations and then search out the more obscure patterns as the need and challenge arise.

Like riding a bicycle, once you know a constellation, it's hard to forget it.

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Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Double Stars around Boötes

On a May evening many years ago, I made my first exploration of the night sky. The only star pattern I could recognize was the Big Dipper, but with a star chart in a book, I used that to discover the bright star Arcturus in the constellation Boötes.

The curve of the Big Dipper's handle leads to Arcturus, the brightest star in the kite-shaped constellation of Boötes. Surrounding Boötes is an amazing variety of double stars. Credit: Starry Night software.

The trick to learning the constellations is to begin with the stars you know, and use them to identify their neighbors. This same technique, known as "starhopping" is the key to discovering all the wonders hidden amongst the stars.

Start, as I did, with the Big Dipper, high overhead as the sky gets dark at this time of year. The stars that form the Dipper’s handle fall in a gentle arc, and if you project that arc away from the Dipper’s bowl, you come to a bright star. This is Arcturus, the third brightest star in the night sky, and the brightest star in the northern sky. Only Sirius and Canopus, far to the south, are brighter.

Arcturus is bright in our sky for two reasons, first because it is relatively close to us, 38 light years away, and secondly because it is inherently a bright star, much brighter than our Sun. Though larger and brighter, it is a slightly cooler star than our Sun, so appears orange to our eyes.

Although Boötes is supposed to be a ploughman in mythology, its pattern of stars most resembles a kite, with Arcturus marking the bottom of the kite where the tail attaches. Notice the little dots over the second “o” in Boötes: this indicates that the two "o"s are supposed to be pronounced separately, as "bow-oo’-tees," not "boo’-tees."

Once you have identified Boötes, you can use its stars to identify a number of constellations surrounding it. Between it and the Big Dipper are two small constellations, Canes Venatici (the hunting dogs) and Coma Berenices (Bernice's hair). To Boötes left (towards the eastern horizon) is the distinctive keystone of Hercules. Between Hercules and Boötes is Corona Borealis (the northern crown) with Serpens Caput, the head of the serpent, poking up from the south.

Although most stars appear to our unaided eyes as single points of light, anyone with access to binoculars or a telescope soon discovers that nearly half the stars in the sky are either double or multiple stars. Some of these are just accidents of perspective, one star happening to appear in the same line of sight as another, but many are true binary stars: two stars in orbit around each other, similar to the stars which shine on the fictional planet Tatooine in Star Wars.

Every star labeled on this map of Hercules, Boötes, and Ursa Major is a double star, worth exploring with a small telescope. Some, like Mizar in the Dipper’s handle, can be split with the naked eye. A closer look with a telescope shows that this is really a triple star. Others require binoculars or a small telescope. Some of the finest are Cor Caroli in Canes Venatici, Izar (Epsilon) in Boötes, Delta Serpentis, and Rho Herculis.

One of the joys of double star observing is the colour contrasts in some pairs. Others are striking for matching colours and brightness. My favorites are stars of very unequal brightness, which look almost like stars with accompanying planets.

Also marked on this chart are three of the finest deep sky objects: the globular clusters Messier 13 in Hercules and Messier 3 in Canes Venatici, and the Whirlpool Galaxy, Messier 51, tucked just under the end of the Big Dipper’s handle. You will probably need to travel to a dark sky site to spot this galaxy. A six-inch or larger telescope will begin to reveal its spiral arms, including the one that stretches out to its satellite galaxy, NGC 5195.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

The Next Pluto Mission: Part I

On July 14th, NASA’s New Horizons spacecraft will fly by Pluto.  It’s among NASA’s most impressive achievements to date.  But what might come next?

New Horizons was launched on January 19, 2006, atop an Atlas V 551 rocket with a Centaur upper stage.  That upper stage, and the New Horizons probe inside, had highest launch speed of any man-made object leaving Earth.  New Horizons crossed the Moon’s orbit just 9 hours after launch - the Apollo astronauts took three days - and reached Jupiter in just over a year  (the Voyager spacecraft took nearly three years).  

Launch of New Horizons. The Atlas V rocket on the launchpad (left) and lift off from Cape Canaveral. New Horizons‍ ' launch was the fastest ever to date, at 16.26 km/s.

New Horizons then used Jupiter’s gravity to slingshot itself onto a hyperbolic trajectory that intersects Pluto just over eight years later.

A composite image of Jupiter and Io, taken on on February 28 and March 1, 2007 respectively. Jupiter is shown in infrared, while Io is shown in true-color.

By the time New Horizons reaches Pluto this July, it will be moving at nearly 14 kilometers per second relative to the planet.  That’s 30% faster than the ISS orbits the Earth.  The probe will flash by Pluto in just a few hours.  New Horizons can’t slow down.  It doesn’t carry enough fuel to enter orbit around, or land on, Pluto.  Nor was it designed to.  Instead, New Horizons will keep flying past Pluto, into a vast outer region of our solar system called the Kuiper Belt.  New Horizons may fly by a few Kuiper Belt Objects after its Pluto encounter, a few candidate KBOs are being selected now.

New Horizons flyby of Pluto and Charon on July 14, 2015. Created with Pluto Safari, a free app for iOS and Android.

But what if New Horizons had been intended to stay longer at Pluto?  After a flyby, the next step in planetary exploration is an orbiter to perform extended surface observations, and then a lander.  Are these things even possible, within current technology?  Pluto is forty times farther from the Earth, than Earth is from the Sun.  Transmissions radioed back by New Horizons take four and a half hours to reach us.  Is there any hope of catching anything more than a fleeting glimpse of such a distant place?

Continued in Part II...

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Asterisms and Constellations

On a recent warm and humid summer night, sky transparency was very poor. Only the brighter stars punched through the water-laden atmosphere but three stars were very prominent. They formed a triangular pattern aptly called the Summer Triangle.

The Summer Triangle begins to rise in the Spring.  As seen from mid-northern latitudes in mid-May near midnight.

The Summer Triangle is an example of an asterism: a group of stars that form a recognizable pattern or shape. The Big Dipper, the Little Dipper and the Great Square of Pegasus are other examples of asterisms.

Asterisms are often confused with constellations and indeed, in ancient times, constellations were mythological figures, animals or objects that were seen in groupings of stars.

The Big Dipper asterism as seen from mid-northern latitudes in mid-May at 10:00 p.m.

Almost everyone in North America is familiar with the Big Dipper which is part of the figure of the Big Bear, or the constellation of Ursa Major.

The Big Dipper asterism belongs to the constellation Ursa Major (Great Bear).

The modern constellation of Ursa Major includes all stars within an area defined by the International Astronomical Union in 1930. So the star 24 Ursae Majoris "belongs" to the constellation Ursa Major even though it is not part of the figure of the bear.

Modern constellation boundaries

Some asterisms such as the Big Dipper, the Sickle of Leo, the teapot of Sagittarius and the Great Square of Pegasus have been known for a long time. All are best appreciated when viewed without optical aid because of their large angular size.

But over the years, people using binoculars and telescopes have come across other striking asterisms and some of these have become well known to amateur astronomers.

Here are some examples.

The Diamond Ring

A tight group of 7th and 8th magnitude stars with Polaris as the "solitaire". Best seen with binoculars in a dark sky or a small telescope with a low power eyepiece showing about a 1° field.

The Coathanger
RA = 19h 25m, Dec = 20° 04'

A group of fifth and sixth magnitude stars in Vulpecula appearing like an upside down coathanger to northern hemisphere observers. Use binoculars for best views.

ET Cluster
RA = 1h 19 m, Dec = 58° 17.5'

This open cluster, also known as NGC 457, is located in Cassiopeia. With a bit of imagination you can make out the figure of ET. (Hint: the two bright stars are ET's eyes). Because of its small size, a telescope is needed to make out this asterism.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Virgo and Her Treasures

Although Virgo is the second largest constellation in the sky (after Hydra), it is poorly known to casual skywatchers. That’s because it contains only one first magnitude star, Spica, and its other stars do not form an easily recognizable pattern like the Big Dipper or Orion.


Virgo is the second largest constellation by area, and is well placed just after dark for exploration. Credit: Starry Night software.

Most of the stars which form the pattern of Virgo are third or fourth magnitude, so are hard to see unless you have dark country skies. City dwellers will need binoculars to see them. Starting from bright Spica there is a chain of four stars to its right, with Porrima (Gamma Virginis) in the middle the brightest. Two stars extend northwards from Porrima, ending with Vindemiatrix.

 Porrima is one of the finest double stars in the sky, but has been hard to split in recent years because the apparent distance between its two components had been closing. It is once again opening up, and its separation of slightly more than 2 arc seconds makes it easy to split in all but the smallest telescopes.

 There are two other double stars in neighboring constellations worth a look: Algorab in Corvus and Zubenelgenubi in Libra, which can be split in binoculars.

If Virgo has few bright stars it makes up for it by containing more galaxies than any other constellation in the sky. It is most famous for containing the Virgo Galaxy Cluster, the nearest galaxy cluster to our own Local Group. Located 60 million light years distant, this is the richest cluster of galaxies in the sky.

The Virgo Galaxy Cluster is an easy starhop from Vindemiatrix. Credit: Starry Night software.

You can locate the Virgo Cluster by sweeping first westward from Spica to Porrima, and then northward to Vindemiatrix. Five degrees west of Vindemiatrix is Rho Virginis at the center of a distinctive Y-shaped group of stars. The Y points upwards to the galaxy cluster. The problem with the Virgo Cluster is not spotting the galaxies, but trying identify which is which. This chart <> will help you to follow the starhop and identify the galaxies. The secret to observing galaxies is to view them from a location with dark skies on a moonless night.

Charles Messier in the Eighteenth Century observed and catalogued eight galaxies in this cluster, plus six more just across the border in Coma Berenices. Two more Messier galaxies are outliers from the main Virgo Group, Messier 49 and Messier 61.

The final Messier galaxy in Virgo is one of the brightest galaxies in the sky and lies slightly nearer than the rest of the Virgo galaxies, 50 million light years distant. This is the famous Sombrero Galaxy, number 104 in Messier’s catalog. It can most easily be found by following a starhop which starts at Gienah, the upper right star in Corvus. In binoculars you can see a long chain of stars extending northeastward from Gienah, ending in a small triangle followed by a group of stars shaped like an arrow. The arrow points right at the Sombrero Galaxy.


This starhop from Gienah in Corvus will lead you directly to the Sombrero Galaxy, Messier 104. Credit: Starry Night software.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Astronomy Concept Diagrams

Explain difficult astronomical concepts with clear, concise diagrams from Starry Night Education. Click on each image to view a larger version.  Feel free to use in your classroom or outreach activities.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Astronomer's Spring Fever

“In spring a young astronomer’s fancy lightly turns to thoughts of…”

It’s spring where I live, a very short-lived season in southern Canada; remnants of snow in the woods, yet I've already swatted my first mosquito. The spring sky is also short-lived because of the Sun’s rapid travel northwards at this time of year. It seems as if winter’s brilliant constellations are replaced by the summer ones in a few short weeks.

The constellation Leo as seen from mid-northern latitudes on May 10 at 9:00 p.m.

Leo galaxies as seen from mid-northern latitudes on May 10 at 9:30 p.m.

It’s now warm enough at night to be able to spend a couple of hours in relative comfort with the stars. This is a good time of year to begin new observing projects. If you’re a newcomer to astronomy, you might enjoy the Royal Astronomical Society of Canada’s “Explore the Universe”program. You don’t have to be a member to participate; just download the program brochure and get started. It will introduce you to the wide variety of objects in the night sky, and won’t take you forever to complete. All you need for most of it is your naked eye, a small pair of binoculars, and a reasonably dark sky.

If you’re more advanced in astronomy, you might take on a more challenging project, such as observing all of the 110 objects in Charles Messier’s catalog of deep sky objects. These include the brightest and best objects in the northern sky, and is considered “basic training” for deep sky observers. All the objects are plotted in Starry Night and SkySafari.

Spring is also the time for spring cleaning. It’s a good time to make sure your astronomical equipment is tuned up and ready to perform at its best. Please note that this usually doesn’t involve cleaning your telescope’s main lens or mirror. Unless you follow very careful procedures, you’re more likely to do damage to your optics than to improve the view. A bit of dust won’t do any harm. What is required is an optical tune-up, called collimation, to make sure your telescope’s optics are properly aligned. This is primarily required by Newtonian reflectors and Schmidt-Cassegrains; refractors and Maksutovs are factory aligned and best left alone unless you really know what you’re doing. Collimation is a painless procedure once you’ve done it a few times; your telescope’s operating manual should contain all the information you need. For Newtonians, a simple collimating eyepiece is a handy aid.

Spring is also a time when many amateur astronomers start leafing through the ads and catalogs of the various manufacturers looking for new hardware to enhance their viewing experience. Every telescope is a compromise of some kind, so many astronomers end up owning more than one telescope. If you already own the large Dobsonian reflector which most of us recommend for beginners, you might consider a small “grab-and-go” refractor which will give you wide field views.

I’m always surprised at how many amateur astronomers own a telescope but not a pair of binoculars. I personally find binoculars to be an indispensable part of my observing “kit.” Not only are they a wonderful observing tool in their own right, giving wide rich fields of view without the hassles of mounts and finders, but they are also an essential part of finding objects by starhopping. A pair of binoculars with the same field of view as your telescope’s finder allows you to practice a starhop comfortably before attempting it with finder and telescope. I own several different sizes of binoculars, but find that I use my 10x50s more than any other size: light in weight, easy to hand hold, and very wide field.

If you become really addicted to binocular views, you might want to invest in a pair of giant binoculars. Because of their weight and magnification, these usually need to be mounted on a tripod.

Most scopes come with one or two basic eyepieces, usually 25 mm and 10 mm Plössl types. These are fine to get you started, but they only hint at the versatility of which an astronomical telescope is capable. After you’re comfortable using these basic eyepieces, you may want to increase your range with a low power wide field eyepiece.

At the other end of the scale, you may want to get up close and personal with the Moon and planets with a specialized planetary eyepiece.

You may choose this spring to embark on a totally new area of astronomy. Many astronomers concentrate on the stars visible at night, but forget the star closest to us, the Sun. A solar filter on the front of your telescope will let you watch sunspots as they rotate across the face of the Sun. You may also want to explore the solar flares and prominences visible with a dedicated Hydrogen Alpha telescope like this:

Another area to explore is astrophotography. Most telescopes can easily be coupled with today’s digital cameras to photograph the Sun, Moon, and bright planets. If your scope has a motorized equatorial mount, you can easily make “piggyback” images by mounting your camera on the piggyback bolt included on the tube rings of many mounts.

However you choose to celebrate spring fever, get out there and enjoy these pleasant spring evenings!

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Telescope Myths

With pleasant spring evenings arriving, many people may be thinking of buying a telescope. There’s a lot of bad advice out there; here are some samples, counterbalanced with the facts.

Myth: Magnification is a good way to judge a telescope

Reality: Any telescope that has interchangeable eyepieces can produce any magnification. The useful magnification on a telescope is much more limited, and depends on the size of the telescope’s aperture (diameter of lens, mirror, or corrector plate). A telescope with 60mm aperture has a range of useful magnifications from about 12x to 120x, no matter what the advertising on the box may say. And a larger telescope, such as an 8” reflector, will have a larger, but still limited range, 40x to 300x. Unless you live in a place with very stable air, such as Florida, 300x will be your upper limit on magnification no matter how big your telescope is.

The best way to compare telescopes is by their aperture. By and large, a telescope with a larger aperture will outperform a telescope with a smaller aperture on every kind of object. The main counterbalancing factors are size, weight and cost. If a telescope is too large to be set up conveniently, it won’t be used as often as a smaller, more convenient scope.

Myth: Refractors are better than reflectors for planetary observation

Reality: Like many myths, there’s a kernel of truth in this one. For a given aperture, a refractor, with its unobstructed aperture, will have better contrast than a reflector, because of the scattering of light caused by having a secondary mirror in the light path. However, this breaks down when faced with the realities of economics and mechanics. An 8” reflector or Schmidt-Cassegrain costs $360 to $2100 and weighs 40 to 75 pounds, complete, and is easily transported in a small car. An 8” refractor costs at least $3500 for the optical tube alone. The tube is eight feet long and would weigh 40 pounds, requiring a mount that costs at least as much as the tube and a permanent observatory to house it in.

Myth: Smaller apertures show more than larger ones when the seeing is poor

Reality: On many occasions I’ve masked my telescopes down under marginal seeing conditions in the hopes of improving their image, but never have I noticed any improvement. All it does is make the image dimmer and reduce the amount of detail visible.

Myth: Smaller apertures work better than large ones under light polluted skies

Reality: I lived for many years in a big city, and never once was I tempted to use anything other than my largest telescope for all kinds of observing. If light pollution reduces what your naked eye sees by three magnitudes, it will also reduce what your telescope sees by exactly the same amount, three magnitudes.

Myth: Faster scopes are better at showing faint objects than slower scopes

Reality: This myth comes from people who are knowledgeable about photography, where “faster” lenses gather more light than “slower” lenses. In telescopes used visually, the focal ratio is irrelevant in terms of how bright the image will appear at a given magnification. Short focal ratios (f/4 to f/6) are generally preferred because they make the scope more compact and allow a wider field of view, while long focal ratios (f/8 to f/15) are preferred because they provide higher magnifications with relatively simple and inexpensive eyepieces. Objects are equally bright in either scope, given identical magnifications.

Myth: I don’t want a Dobsonian: it doesn’t look like a real telescope

Reality: Despite the fact that the Dobsonian design offers the most “bang for the buck” in any telescope size, some people seem to be turned off by its looks. It doesn’t have a lens at the top of the tube, and the mount looks more like a cannon than a precision instrument.

But, take a look at any modern research telescope, such as the Subaru on Mauna Kea:

That sure looks more like my Dob than like my grandfather’s refractor!

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Astronomical Audio Pronunciation Guide

Some astronomical monikers truly do seem alien, and ensuring correct pronunciation can be hazardous for even the most advanced educator. Starry Night Education is here to help with our Audio Pronunciation Guide for the top 500 most commonly mispronounced astronomical objects, from Acamar through Zubeneschamali.

Choose your category:
asteroids
constellations
planets
meteors
stars
Asteroids
Constellations
Planets & Moons
Meteor Showers
Stars

     
Click the name to hear the correct pronunciation.

Asteroids
 
 
Name
Pronunciation
 
ANN-FRANK
 
a-PAW-fis
 
a-STREE-a
 
BACK-us
 
BRAIL
 
SEER-eez
 
e-JEER-ee-a
 
EER-os
 
ewe-NOM-ee-a
 
FLOOR-a
 
for-TUNE-a
 
HEE-bee
 
hy-GEE-a
 
eye-REE-nee
 
EYE-ris
 
JEW-noe
 
ka-LYE-o-pee
 
lew-TEE-sha
 
ma-SALL-ee-a
 
mel-POM-e-nee
 
MEE-tis
 
PAL-as
 
par-THEN-o-pee
 
SYE-kee
 
SIL-vee-a
 
the-LYE-a
 
THEE-tis
 
VES-ta

Constellations
 
 
Name
 
Pronunciation
 
an-DROM-eh-da
 
ANT-lee-uh
 
APE-us
 
ack-KWAIR-ee-us
 
ack-WILL-lah
 
AY-rah
 
AIR-ease
 
or-EYE-gah
 
bow-OH-tease
 
SEE-lum
 
ca-MEL-oh-PAR-dal-iss
 
KAN-surr
 
KAN-es veh-NAT-ih-see
 
KANE-es MAY-jer
 
KANE-es MY-ner
 
CAP-rih-CORN-us
 
car-EE-na
 
KASS-ee-oh-PEE-ah
 
sen-TOR-us
 
SEE-fee-us
 
SEE-tus
 
kah-ME-lee-un
 
SIR-sin-us
 
ko-LUM-ba
 
CO-ma bare-uh-NYE-sees
 
coe-ROW--nah ow-STRAHL-iss
 
coe-ROW--nah BOR-ee-AL-iss
 
CORE-vuss
 
CRAY-ter
 
Kruks
 
SIG-nus
 
del-FYE-nus
 
doh-RAY-doh
 
DRAY-ko
 
eh-KWOO-lee-us
 
eh-RID-uh-nuss
 
FOR-naks
 
GEM-in-eye
 
GROOS
 
HER-kyou-leez
 
hor-uh-LOW-gee-um
 
HY-druh
 
HY-drus
 
IN-dus
 
la-SIR-ta
 
LEE-oh
 
LEE-oh MY-ner
 
LEE-puss
 
LEE-bra
 
LOUP-us
 
links
 
LIE-rah
 
MEN-sa
 
MY-krow-SKOH-pee-em
 
mon-OSS-er-us
 
MUSS-ka
 
NOR-ma
 
OCK-tens
 
Oaf-ih-YOU-kus
 
oh-RYE-un
 
PAY-vo
 
PEG-uh-suss
 
PURR-see-us
 
FEE-nix
 
PICK-tor
 
PIE-sees
 
PIE-sees oss-TREE-nus
 
PUP-iss
 
PICK-sis
 
reh-TICK-yuh-lum
 
suh-JIT-uh
 
sa-jih-TARE-ee-us
 
SKOR-pee-uss
 
SKULP-tor
 
SCOOT-um
 
SIR-pens CAP-ut
 
SIR-pens KAW-dah
 
SEX-tens
 
TOR-us
 
tell-es-SCOPE-ee-um
 
tri-ANG-yuh-lum
 
tri-ANG-yuh-lum aus-TRAY-lee
 
too-KAY-nah
 
URR-sah MAY-jer
 
URR-sah MY-ner
 
VEE-la
 
VER-go
 
VO-lans
 
vul-PECK-yoo-la

Planets & Moons
 
 
Name
Pronunciation
 
ah-DRAHS-tee-ah
 
et-NEE
 
ah-mal-THEE-ah
 
a-NAN-kee
 
AIR-ee-el
 
AT-lus
 
aw-TON-oe-ee
 
be-LIN-dah
 
bee-AHNK-uh
 
KAL-e-ban
 
ka-LIRR-o-ee
 
ka-LIS-toe
 
ka-LIP-soe
 
KAR-mee
 
kal-DEE-nee
 
CARE-en
 
core-DEAL-ya
 
KRESS-e-da
 
DYE-mos
 
DES-de-MOAN-a
 
de-SPEEN-a
 
dye-ON-ee
 
URTH
 
EE-lahr-ah
 
en-SELL-ah-dus
 
EPP-e-ME-thee-us
 
err-IN-o-mee
 
EE-ris
 
ewe-AN-thee
 
ewe-POUR-ee-e
 
you-ROE-pah
 
ewe-RID-o-mee
 
GAB-ree-ell
 
GAL-aTEA-a
 
GAN-eh-meed
 
har-PAL-e-kee
 
he-LEAN
 
her-MIP-ee
 
HIM-ah-lee-ah
 
hye-PER-ee-on
 
ee-AHP-eh-tus
Io
 
EYE-oh
 
EYE-o-KAS-tee
 
eye-SON-oe-ee
 
JAY-nus
 
JEW-lee-ette
 
JEW-pi-ter
 
KAY-lee
 
KAL-e-kee
 
la-RISS-a
 
LEE-dah
 
lis-ih-THEE-ah
 
MARZ
 
MEG-a-KLYE-tee
 
MIRK-you-ree
 
MEE-tis
 
MYE-mus
 
mi-RAN-dah
 
moon
 
NYE-ad
 
NEP-toon
 
NAIR-ee-id
 
OH-ba-ron
 
oh-FEEL-ya
 
or-THOE-see-e
Pan
 
PAN
 
pan-DOOR-ah
 
pa-SIF-ah-ee
 
PAS-e-thee
 
FOE-bos
 
FEE-bee
 
PLOO-toe
 
POR-sha
 
prak-SID-e-kee
 
pro-MEE-thee-us
 
PRO-per-oe
 
PRO-tee-us
 
PUCK
 
KWA-oh-ar
 
REE-a
 
ROS-a-lind
 
SA-turn
 
SET-e-bus
 
se-NO-pee
 
SPON-dee
 
ste-FAA-noe
Sun
 
sun
 
SICK-o-RACKS
 
tay-IJ-e-tee
 
tah-LES-toe
 
TEE-this
 
tha-LASS-a
 
THEE-bee
 
the-MISS-toe
 
Thy-OE-nee
 
TYE-tun
 
tye-TAIN-ee-ah
 
TRING-kew-loe
 
TRY-ton
 
UM-bree-el
 
YOU-rah-nus
 
VEE-nus

Meteor Showers
 
 
Name
Pronunciation
 
AY-tah AK-wa-rids
 
GEM-e-nids
 
LEE-o-nids
 
LYE-rids
 
north TOR-ids
 
o-RYE-o-nids
 
PUR-see-ids
 
kwa-DRAN-tids
 
south DEL-tah AK-wa-rids
 
south TOR-ids

Stars
 
 
Name
Pronunciation
 
AH-kuh-mar
 
AK-er-nar
 
A--krucks
 
ACK-you-benz
 
ad-HAR-a
 
al-KAP-rah
 
all-NAYR
 
all-NEE-yaht
 
all-soo-HAIL
 
al-BAL-dah
 
al-BEE-ri-oh
 
al-CHIH-ba
 
AL-kor
 
all-SYE--o-nee
 
al-DEB-ah ran
 
al-DER-a-min
 
al-da_FER-a
 
All-firk
 
all-JED-ee
 
al-JEN-nib
 
al-GEE-bah
 
al-GEEB-bah
 
AL-gall
 
ALL-gor-ab
 
al-HAY-nah
 
AL-lee-oth
 
AL-kade
 
al-ka-LOOR-ops
 
ALL-maaz
 
ALL-mahk
 
all-NAH-zul
 
ALL-nil-ahm
 
ALL-nit-ahk
 
AL-fard
 
al-FECK-ah, JEM-a
 
AL-fer-rats
 
all-RAH-kiss
 
all-RESH-ah
 
all-SHAIN
 
AL-tair
 
ALL-tays
 
al-TARF
 
al-TERF
 
 
al-UDE-rah
 
a-LOOL-ah ow-STRAH-liss
 
a-LOOLah bor-ee-AH-liss
 
ALL-zirr
 
UNG-ka
 
ANG-kah
 
an-TAIR-ease
 
arc-TOUR-russ
 
AR-kub
 
AR-kub
 
AR-kub PREE-or
 
AHR-neb
 
ah-SELL-a
 
ah-SELL-us ow-STRALICE
 
ah-SELL-us bore-ee-AL-is
 
ah-SELL-us
 
ah-SELL-us
 
ah-SELL-us
 
ass-mid-ISS-kee
 
ass-pid-ISS-kee
 
AH-tik
 
AT-las
 
AH-tree-a
 
 
AV-i-or
 
AH-za
 
ba-HAHM
 
BARN-ards star
 
BUT-en KYE-tos
 
BYED
 
BEL-la-trix
 
BET-el-jooz
 
boh-TAYN
 
can-OH-pus
 
kah-PELL-ah
 
KAF
 
CASS-ter
 
SEB-all-rye
 
ke-LAY-no
 
CHAH-ra
 
KERT-ahn,
 
core-ca-ROLE-ee
 
COOR-sah
 
DAH-bee
 
DEN-ebb
 
DEN-ebb al-JEE-dee
 
DEN-ebb
 
DEN-ebb
 
DEN-ebb KAY-tos
 
de-NEB-oh-la
 
DYE-a-dem
 
JOOB-a
 
DOOB-huh
 
ED-a-sick
 
e-LEK-tra
 
EL-noth
 
EL-ta-nin
 
EEN-if
 
er-RYE
 
e-RAHK-is (mu Draconis)
 
FO-mal-oh
 
fur-ROOD
 
GAK-kruks
 
JAW-sahr
 
JEEN-ah
 
GIRR-tahb
 
go-MAY-sah
 
GRAH-fi-us
 
GROOM-bridge
 
"
 
GROO-mi-um
 
HAH-dahr
 
HAM-al
Han
 
HAN
 
 
 
HEE-dus
 
HEE-dus
 
HOH-mahm
 
EYE-zar
 
JAB-bah
 
KAFF-al-JID-mah
 
KOWSS ow-STRAH-liss
 
KOWSS bor-ee-AH-liss
 
KOWSS me-RID-i-an-AL-is
 
KYED
 
kit-AL-fa
 
KOE-cab
 
core-ne-FOR-uss
 
 
KOOR-hah
 
la su-PURR-ba
 
la-KA-ya
 
la-KA-ya
 
la-LAHND
 
LAY-soth
 
MAH-ya
 
MAR-fick
 
MAR-kab
 
MAH-tahr
 
meb-SOO-tah
 
meg-REZ
 
MAY-sah
 
mek-BOO-dah
 
men-KAH-li-nan
 
men-KAHR
 
men-KENT
 
men-KIB
 
MER-ak
 
MER-o-pee
 
mess-AHR-tim
 
mee--a-PLASS-id-uss
 
mim-OH-sah, BAY-cruks
 
MIN-kar
 
MIN-ta-ka
 
MEE-ra
 
MIRR-ahk
 
MERE-fak
 
MERE-zam
 
MYE-zahr
 
MOOL-if-ayn
 
MOO-frid
 
MUSS-id-a
 
nar-AL-safe
 
NOWSS
 
nah-SHE-rah
 
NECK-ahr
 
nih-HALL
 
NOH-dus
 
NUN-kee
 
noo-SAH-kahn
 
Oaf-ih-YOU-kus
 
FEYE-et
 
FEK-da
 
ferk-AHD
 
PLAY-o-nee
 
poe-LAIR-is
 
POL-lucks
 
pour-EE-mah
 
PRO-see-on
 
PRO-puss, TAY-zhaht PRYE-or
 
RAH-sa-luss
 
rah-sell-GAYTH-ee
 
RAHS-al-haig
 
RAHS-al-MOTH-al-ah
 
REG-you-luss
 
RYE-jel
 
RYE-jel ken-TAW-russ
 
ROH-ta-nev
 
ROOK-baht
 
ROOK-baht
 
SAH-bik
 
sah-DUCK-be-ah
 
sah-dul-BAH-ree
 
sah-dul-MEL-ik
 
sah-dul-su-OOD
 
SADE-der
 
SAFE
 
SAHR-goss
 
SAHR-in
 
SHEE-at
 
SHED-er
 
SEG-in
 
seg-EEN-us
 
SHOWL-a
 
SHEL-ee-yak
 
SHARE-ah-tan
 
SEER-ee-us
 
SKAHT
 
SPEE-ka
 
STER-o-pee
 
swah-LOH-sin
 
soo-HALE-al-MOO-liff
 
SOOL-a-faht
 
SIRM-a
 
TAH-lith-a
 
THA-ni-ya ow-STRAH-liss
 
THA-ni-ya bor-ee-AH-liss
 
TAHR-ah-zed
 
TAY-get-a
 
teg-MEEN-e
 
TAY-zhaht pos-TER-i-o
 
THOO-bahn
 
tra-PEEZ-i-um
 
tra-PEEZ-i-um
 
tra-PEEZ-i-um
 
tra-PEEZ-i-um
 
uh-NOO-kul-lye
 
VEY-ga
 
vin-de-mee-AY-tricks
 
wah-SAHT
 
WUZ-un
Wei
 
 
WEZ-en
 
YED pos-TER-i-or
 
YED PRYE-or
 
zah-NYE-a
 
ZAW-rahk
 
zah-vee-JAH-vah
 
ZOSS-mah
 
zoo-BEN-el-AK-rab
 
zoo-BEN-el-je-NEW-bee
 
zoo-BEN-esh-ah-MAL-ee

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

The Lure of Variable Stars

I’m a sucker for action. I love change. My favorite planet is Jupiter because of its rapid rotation, ever-changing moons, and volatile cloud features. I love watching Near Earth Asteroids and comets as they move across star fields. Recently I’ve become addicted to watching solar flares and prominences in rapid action with my solar telescope. But most of all, I love to observe variable stars.

All stars vary in brightness to some degree. Even our Sun, which seems so stable, changes its brightness as more or less of its surface is obscured by sunspots. But there are stars in the sky that undergo vast changes in brightness and color. Many are highly unpredictable in their behavior, and need years of study to uncover the mechanisms that drive them.

The Variable Zoo

The most famous are the novas and supernovas which suddenly shoot up from obscurity to prominence. Supernovas are relatively rare in our neighborhood. The last one was over 400 years ago in 1604. Novas are more common, several being observable in any given year.

Some stars appear to vary for purely mechanical reasons. These are called eclipsing binaries: two stars in a close orbit where one star eclipses the other, as regular as clockwork. Algol in the constellation of Perseus is a famous example of an eclipsing binary.

Other stars expand and contract slowly because of processes going on within them. The most common of these “pulsating variables” are long period variable stars like Mira in the constellation Cetus. Mira is larger in diameter than the orbit of Mars, and changes size, brightness, and color over a period of just under a year. It ranges over nearly six magnitudes in brightness, meaning that at its brightest, it is a hundred times brighter than when it’s at its dimmest. Another group of pulsating variables is called the Cepheids, named after the star Delta Cephei. These have much shorter periods than the Miras, ranging from 1 to 70 days, and their period is closely tied to their luminosity, which has led to their use as measuring sticks to determine the distance of globular clusters and galaxies.

Another group of variable stars is called “cataclysmic variables.” These include novas, supernovas, and the so-called “dwarf novas.” These last are the stars that interest me the most because they show the most action. My favorite is SS Cygni (TCY 3196-723-1), located close to the open cluster Messier 39. This star normally sits around twelfth magnitude, just visible in a small telescope, but every few weeks it shoots up unpredictably to about eighth magnitude. If you’re lucky enough to catch it in outburst, you can actually see it get visibly brighter. Stars like SS Cygni are actually close double stars consisting of a red dwarf and a white dwarf. The white dwarf is surrounded by a disk of gas stolen from the red dwarf which is drawn down into the white dwarf where it ignites, causing the sudden outburst in brightness.

 

Observing Variable Stars

Professional astronomers realized over a century ago that there were more variable stars in need of study than they could handle, so they enlisted the aid of amateur astronomers to monitor the brightness of a number of stars well suited to amateur observation: stars which changed in magnitude over a wide range and which took a long period to complete their cycle of brightness. For many years this work required no more than a telescope and a good set of charts, and such simple visual observations are still useful today, although nowadays amateurs have access to photoelectric photometers and CCD cameras which are capable of studying just about any star. The American Association of Variable Star Observers acts as a central clearing house for all sorts of amateur variable star observations, providing instruction, charts, and other support, and giving amateurs a simple online system for recording their observations.

Why observe variable stars? Mainly because it’s fun! You never know from night to night what you are going to find…remember what I said about action? No special equipment is needed other than a set of star charts which plot the variable star and give the brightness of non-variable stars around it, which are used to estimate the brightness of the variable.

If you are a deep sky observer, you already have one of essential skills of a variable star observer: you know how to locate objects in the sky. It doesn’t matter how you do it. I used traditional starhopping for several years, but now I use my Orion SkyQuest XT6’s IntelliScope setting circles to locate my variables. Once you’ve located the variable, you estimate its brightness as compared to other stars on the chart, and record the time of the observation. With a little practice you can make estimates to within a tenth of a magnitude. You can then log onto the AAVSO’s web site and enter your observation. Within ten minutes it will be moved into their database of over ten million observations, and you can see your observation on a light curve along with those of hundreds of other observers around the world. What could be neater?!

Unlike most of the observations amateur astronomers make, variable star observations have a serious side. By making a numerical estimate of the brightness of a star at a particular point in time, you are logging a piece of scientific data. The AAVSO maintains records online of every observation submitted to them over the past hundred years, keeping the records available to researchers around the world.

On a typical night, I’ll observe about a dozen stars from “my” list of about sixty stars visible at different times of year.

I keep finder charts along with the AAVSO charts in plastic sleeves in a loose-leaf binder, so that everything I need is close at hand. Since you never know ahead of time how bright a variable is going to be, you need to have a complete set of charts for each star; these can be downloaded from the AAVSO web site:

The biggest challenge in finding a variable star is that you’re looking for something that may be quite bright, or may be below the magnitude limit of your telescope, totally invisible to you. So what you look for is the star field, the pattern of stars surrounding the variable. Once you’ve found the field, you then check to see how bright the variable is. You then consult your AAVSO charts to see which stars are closest in brightness to the variable. Comparison stars on the charts are marked with their brightness to the nearest tenth of a magnitude. Because a decimal point might be confused with a faint star, they are left out, so that a 9.7 magnitude star is marked “97” and a 11.4 is marked “114” on the chart. You try to find a couple of stars, one slightly brighter than the variable, one slightly fainter, and then estimate where the variable falls between them.

Equipment for variable star observing

For visual observing as I have described above, the equipment needs are very simple. There are many variable stars within range of a pair of small binoculars, and some that can be observed with the naked eye alone. On the other hand, access to a large telescope lets you follow stars that become very faint at minimum.

I have found it advantageous to use eyepieces with a wide field of view, since they show me more of the sky at any given magnification, and let me see more comparison stars without having to move the telescope about.

My current strategy is to survey “my” variables using my Celestron 6" SCT telescope. I’ve programmed the controller with the coordinates of my variables, so I can quickly move through the list. Any variables which are currently too faint to be observable with the 6”, I revisit the next night with my larger 11” Dobsonian.

Where to start?

If you’re still not sure whether variable star observing is for you, I’d recommend reading Starlight Nights by Leslie Peltier (Sky Publishing). Peltier was the finest variable star observer of the 20th century, and his book is an entertaining introduction to a wonderful man and his love of the stars. It’s probably my very favorite astronomy book.

The AAVSO web site includes everything you need to get started. It has a complete observing manual, a list of good stars to start on, and all the charts you will need, all free of charge. Visit http://www.aavso.org

I’d recommend starting on stars that are easy to find and visible all year round, such as these stars in and around the Big Dipper:

A final warning though: variable star observing is highly addictive. Variable star observers probably spend more time at the eyepiece than any other amateur astronomers because, unlike deep sky or planetary observing, they are not dependent on dark skies or steady seeing. For years I carried out regular variable star observing every clear night from the middle of a large city, even when the Moon was full. The only thing that can stop you is clouds!

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. ​

Saturn Through the Ages

On May 23rd, Saturn will reach opposition — the closest it will be to Earth in 2015.

Saturn, the original Load of the Rings.

Saturn can be viewed in the morning sky until May 23, when it moves into the evening sky. From November to the end of the year it will be behind the Sun.

Looking south-east on May 23, 2015 at 11:00 p.m. from mid-northern latitudes.

The rings are now widely open, making them easy to see in any telescope magnifying more than about 30x. Saturn’s largest moon Titan is readily visible in a small telescope, and several more moons may be seen in larger telescopes. At opposition, the planet’s equatorial angular diameter will be 19 arc seconds, its rings being 42 arc seconds across.

As you peer through your eyepiece and ponder the ringed planet with the benefit of our modern understanding of science, consider how perplexing Saturn must have been to ancient people whose instruments and grasp of nature were at their infancy.

Eyepiece view (10 arc minutes) of Saturn on May 23, 2015.  The planet’s equatorial angular diameter will be 19 arc seconds, its rings being 42 arc seconds across.

In our feature article below, “Saturn Through the Ages” — a departure from our usual technical take on the universe — we will be returning to times past to explore a piece of the puzzle that highlights our search for knowledge and meaning.

Saturn Through the Ages  

Throughout human history, we have looked to the light of the heavens to illuminate our role on Earth. Next time you are star gazing, consider all of the people throughout time and across the world who have reflected upon the same celestial bodies, conducting their nightly dance across our sky.

Our study of the celestial sphere has brought us understanding of physical and mathematical principles, models for society and perhaps fundamentally, a comforting sense of order. It is the human imagination however, and our quest to find a meaning behind this order, that led us to create a screenplay of the night sky. For millennia we have told our own tale through the guise of a heavenly cast of characters. Because celestial mythology is common throughout many cultures, these stories reveal our discoveries of the human condition.

In the upcoming month, many of us will be gazing at the planet Saturn in the northeastern sky. Perhaps due to a planet’s slow trek through our heavens, the stories we've told about Saturn often involve the passage of time and inevitable fate. We've expressed through Saturn both our appreciation for life and our fear of time's cruel and inescapable quality.

In ancient Mesopotamia, they prayed to Saturn as the Lord of Death, appealing to him thus:

“O Lord Saturn
whose name is august
whose power is widespread
whose spirit is sublime
O Lord Saturn
the cold, the dry, the dark, the harmful…
crafty sire who knowest all wiles
who are deceitful, sage and understanding
who causest prosperity and ruin
happy or unhappy is he whom thou makest such.”

In ancient Rome, Saturn was an agricultural god, a harvest deity. Controlling our fate through the success of our crop, he was celebrated in times of bounty and appealed to when times were hard. The Golden Age of Saturn, an ideal era of equality and abundance, was memorialized during the mid-winter festival of Saturnalia. A time of feasts and gifts from which we can trace rituals of modern day Christmas. During the celebration, a man chosen to represent the god was attentively fêted, only to be sacrificed on the final day of the festival. Try as we have to sway him however, we are all equally powerless before the forces personified by Saturn. 

In Hindu mythology, Saturn appears as the god Sani, holder of the secrets of fate. One could predict the future through use of a Saturn diagram, which represents the planet’s path through our skies. This god is so malevolent that a single glance from the evil-eyed deity burned off the head of the infant Ganesa, god of good fortune and prosperity. Associated with childhood disease, Sani demonstrates that not even a god’s luck can stand against the inevitability that Saturn represents.

Though we may wish it otherwise, nothing in our human existence remains static; nothing escapes the passage of time. Falcon-headed Horus, Saturnine god of the ancient Egyptians, succeeded his father Osiris when he was dethroned, marking the beginning of a new regime. As all change implies death of the old, we tell our tales of Saturn to reconcile ourselves to the necessity of welcoming the new. 

Cronos, Saturn-god of ancient Greece, whose name may originally have referred to his universal governance (from the verb kreno), became known as Father Time. Cronos not only overthrew and replaced his father, but consumed each of his own children at birth, much as time itself consumes all that it creates. Demonstrating the universality of this principle, Cronos himself was ultimately dethroned by his offspring, making way for a new era.

Through our creation of Saturn mythology, we attempt to explain our relationship to fate, time and death. Our ability to perceive these issues is fundamental to our very humanity. When next gazing at Saturn in the night sky, perhaps you will see not only a wonder of the cosmos, but also the history of humanity’s struggle to find meaning therein.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Sky Events For May 2015

Moon Phases

Full Moon

Sunday, May 3, 11:42 p.m. EDT

The Full Moon of May is known as the “Milk Moon,” “Flower Moon,”  or “Corn Planting Moon.” It rises around sunset and sets around sunrise; this is the only night in the month when the Moon is in the sky all night long. The rest of the month, the Moon spends at least some time in the daytime sky.

Last Quarter Moon

Monday, May 11, 6:36 a.m. EDT

The Last Quarter Moon rises around 2 a.m. and sets around 1 p.m. It is most easily seen just after sunrise in the southern sky.

New Moon

Sunday, May 18, 12:13 a.m. EDT

The Moon is not visible on the date of New Moon because it is too close to the Sun, but can be seen low in the East as a narrow crescent a morning or two before, just before sunrise. It is visible low in the West an evening or two after New Moon.

First Quarter Moon

Monday, May 25, 1:19 p.m. EDT

The First Quarter Moon rises around 1 p.m. and sets around 2:15 a.m. It dominates the evening sky.

Observing Highlights

Mercury at greatest elongation

Thursday, May 7, evening twilight

This is the best evening apparition of Mercury this year for observers in the northern hemisphere. Use Venus to help you locate it. Mercury is most easily located by sweeping with binoculars, but once you’ve located it, you should be able to see it with your unaided eyes

Uranus and the Moon

Friday, May 15, dawn

The Moon will pass just south of the Uranus just before sunrise.

Double shadow transit on Jupiter

Wednesday, May 20, 8:06–8:35 p.m. EDT

The shadows of Io and Ganymede will be on opposite limbs of Jupiter, while the moons Io and Callisto will be central on the disk.

Saturn at opposition

Friday, May 22, 10 p.m. EDT

Saturn will be in opposition to the Sun.

Note how most of Saturn’s moons are in the same plane as the rings, except for Iapetus, whose orbit is tilted 8.3 degrees. At opposition, Iapetus is close to maximum elongation towards the west, while Tycho is close to maximum elongation towards the east.

Double shadow transit on Jupiter

Wednesday, May 27, 10:01 p.m.–12:18 a.m. EDT

The shadow of Io chases the shadow of Ganymede across the face of Jupiter, catching up with it and passing it at 11:48 p.m. EDT. The Great Red Spot will also cross Jupiter’s disk during this period.

Planets

 Mercury is well placed for northern hemisphere observers in the evening twilight sky for the first three weeks of May.

Venus shines high in the western sky after sunset.

Mars moves from Aries to Taurus on May 3, too close to the Sun to be visible.

Jupiter is well placed in the evening sky all month.

Saturn is just north of Scorpius’ “claws.” At opposition on May 22, it is visible all night.

Uranus rises just before the Sun in Pisces.

Neptune is in the eastern morning sky in the constellation Aquarius.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Mercury at its Best

Now that Pluto has been demoted to a dwarf planet, Mercury is the smallest of the eight planets. With a diameter of 3032 miles (4879 km.), it is slightly more than a third of the diameter of Earth, and smaller than the solar system’s two largest moons, Ganymede and Titan. Because of its tight orbit around the sun, Mercury never strays far into the night sky, peeping tantalizingly over the horizon a few times a year. The next two weeks will be your best chance for seeing Mercury in evening twilight this year.

Timing is the secret for catching sight of Mercury. Try too early, and its tiny speck of light will be lost against the twilight sky. Try too late, and Mercury will be too close to the horizon. I’ve found the best time to be about half an hour after sunset. Binoculars are helpful in initially spotting Mercury, but once located in binoculars you should be able to see it with the unaided eye.

Currently Venus is shining brightly in the evening sky, and it can be a helpful guide to spotting Mercury, about two-thirds of the way down towards the horizon, and slightly to your right. Don’t confuse it with nearby Aldebaran, which will have a noticeably reddish color and will probably twinkle, while Mercury shines with a more steady light.

On the evening of Thursday, May 7, Mercury will be at its farthest from the Sun, making the next two weeks the best time this year for observers in the northern hemisphere to spot this elusive little planet. Credit: Starry Night software.

On the evening of Thursday, May 7, Mercury will be at its farthest from the Sun, making the next two weeks the best time this year for observers in the northern hemisphere to spot this elusive little planet. Credit: Starry Night software.

In a telescope, Mercury is a disappointing sight. Like Venus, Mercury exhibits phases as it passes between us and the sun. At present it is slightly gibbous. On Saturday, May 2, it will look just like a miniature first quarter moon. After that, it will assume a crescent shape.

Because Mercury is always seen close to the horizon, it is a challenge to see its surface markings, even in a powerful telescope. Serious observers of Mercury prefer to observe it in the daytime sky, now relatively easy to do because of computerized telescopes. But always be very careful when observing with the sun above the horizon, because even the briefest view of the sun in a telescope will do permanent harm to your eyes.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Starry Night 7, eclipses and ... Elmo

Like most two years olds, my daughter loves Elmo. Something about his high-pitched voice and ever-present smile I guess.

Parents innately learn to tune him out, probably to moderate the risk of going insane listening to that same shrill voice on reruns day after day.

One episode that sticks out in my mind, today more than ever perhaps, puts Elmo in a room with none other than David Beckham. The short ends after Elmo, who pesters Becks to teach him to dribble a soccer ball on his head, learns a new word... Persistence.

Persistence is an extremely important quality, and some might say a disappearing quality these days. It goes hand-in-hand with patience I think, something we can all agree is becoming scarce in this age of on-demand everything.

Persistence, as in the case of Elmo and Becks, often pays off.

Over the past few weeks, I've been involved in an exchange over the accuracy of Starry Night's eclipse predictions. One of our "power users" (who shall remain nameless for now) reported what he believed to be an issue with our calculations. They just didn't match up exactly with what NASA (and other government sites) were reporting.

The discrepancy was small; in fact, the timings were exact, to the sub-second but the sizes of the Earth's shadows (both the umbra and penumbra) were too small by a very small but noticeable fraction.

Normally no-one would even notice this, but in this case it changed our prediction for the April 4th, 2015 eclipse from a Total (as reported by NASA) to a Partial eclipse. That made all the difference to a few people.

I sit down at my 'puter. "I'll figure this out", I say to myself confidently:

  • Were we perhaps using an old or imprecise value for the Earth's diameter? Nope. That was in agreement with the USGS.
  • Were we taking the oblateness of the Earth into account? Yup. A precise calculation there too.
  • Was this somehow rounding or another error in calculation? Nope. Everything seems to check out.

After a few hours of this, I checked with my confrere, Bill (our SkySafari developer) to see if they had the same discord with NASA predictions. They did! And even better (worse, it turns out) both Starry Night, and SkySafari, two completely independently created applications, gave almost exactly the same result!

That sealed it for me. Other matters were more pressing. NASA could be wrong too (note that it's not insane to believe this, the pages we were referring to were intended for the public, maintained by a summer student and weren't necessarily vetted by anyone), or could have used slightly different values for the radius of the Earth. Were THEY accounting for the oblateness? Doubts and lack of information made it difficult.

After presenting my findings to Keiron, our head of support, I let the issue go.

Lots of other stuff to work on.

Again, the power user, and Keiron came back to me. Why were our predictions different? We claim arcsecond precision in our planet and moon positions. How could we make that claim if this discrepancy existed?

Again, I chatted with Bill. He said he had been talking with Keiron too. I Don't know what this annoying user thinks he knows that we don't. What could it be? "The Earth's atmosphere?" Says Bill. I dunno. Does NASA take it into account? It's not clear from their site. How can we compare if they don't say? The discrepancy is so small.

Lots of other stuff to work on.

Again, an email from Keiron. "Aren't you busy?" I think to myself. I open it, a curt reply, ready at my fingertips. This time, the message comes with a link.

"Do you think the Danjon rule explains the difference?" he asks:

http://www.eclipsewise.com/oh/oh-help/LEshadow.html

...

Holy s*&t!

...

Not just a clear explanation of what, how, and by how much the Earth's atmosphere contributes to the shadow, but authored by Fred Espenak himself, The Godfather of eclipse predictions! 

This page on the eclipse, with nicely outlined parameters showed something called "Shadow Enlargement":

http://www.eclipsewise.com/lunar/LEprime/2001-2100/LE2015Apr04Tprime.html

... with a link to a clear explanation of what the Danjon shadow rule is, and its value.

It turns out that the Earth's atmosphere contributes around 1/85 (just over 1%) to the diameter of the Earth's shadow... an effect that we were NOT taking into account in Starry Night or SkySafari... but are now! (SN version 7.1.2+, SkySafari ).

Starry Night has been around for almost 20 years in some form or another, and we have never taken this into account, until now.

We could all learn a little from this power user and Keiron (and Elmo for that matter). It pays to be persistent! 

Thanks for keeping at it guys. Starry Night is that much better for it.

After a few hours of this, I checked with my confrere, Bill (our SkySafari developer) to see if they had the same discord with NASA predictions. They did! And even better (worse, it turns out) both Starry Night, and SkySafari, two completely independently created applications, gave almost exactly the same result!

That sealed it for me. Other matters were more pressing. NASA could be wrong too (note that it's not insane to believe this, the pages we were referring to were intended for the public, maintained by a summer student and weren't necessarily vetted by anyone), or could have used slightly different values for the radius of the Earth. Were THEY accounting for the oblateness? Doubts and lack of information made it difficult.

After presenting my findings to Keiron, our head of support, I let the issue go.

Lots of other stuff to work on.

Again, the power user, and Keiron came back to me. Why were our predictions different? We claim arcsecond precision in our planet and moon positions. How could we make that claim if this discrepancy existed?

Again, I chatted with Bill. He said he had been talking with Keiron too. I Don't know what this annoying user thinks he knows that we don't. What could it be? "The Earth's atmosphere?" Says Bill. I dunno. Does NASA take it into account? It's not clear from their site. How can we compare if they don't say? The discrepancy is so small.

Lots of other stuff to work on.

Again, an email from Keiron. "Aren't you busy?" I think to myself. I open it, a curt reply, ready at my fingertips. This time, the message comes with a link.

"Do you think the Danjon rule explains the difference?" he asks:

http://www.eclipsewise.com/oh/oh-help/LEshadow.html

...

Holy s*&t!

...

Not just a clear explanation of what, how, and by how much the Earth's atmosphere contributes to the shadow, but authored by Fred Espenak himself, The Godfather of eclipse predictions! 

This page on the eclipse, with nicely outlined parameters showed something called "Shadow Enlargement":

http://www.eclipsewise.com/lunar/LEprime/2001-2100/LE2015Apr04Tprime.html

... with a link to a clear explanation of what the Danjon shadow rule is, and its value.

It turns out that the Earth's atmosphere contributes around 1/85 (just over 1%) to the diameter of the Earth's shadow... an effect that we were NOT taking into account in Starry Night or SkySafari... but are now! (SN version 7.1.2+, SkySafari ).

Starry Night has been around for almost 20 years in some form or another, and we have never taken this into account, until now.

We could all learn a little from this power user and Keiron (and Elmo for that matter). It pays to be persistent! 

Thanks for keeping at it guys. Starry Night is that much better for it.

Again, I chatted with Bill. He said he had been talking with Keiron too. I Don't know what this annoying user thinks he knows that we don't. What could it be? "The Earth's atmosphere?" Says Bill. I dunno. Does NASA take it into account? It's not clear from their site. How can we compare if they don't say? The discrepancy is so small.

Lots of other stuff to work on.

Again, an email from Keiron. "Aren't you busy?" I think to myself. I open it, a curt reply, ready at my fingertips. This time, the message comes with a link.

"Do you think the Danjon rule explains the difference?" he asks:

http://www.eclipsewise.com/oh/oh-help/LEshadow.html

...

Holy s*&t!

...

Not just a clear explanation of what, how, and by how much the Earth's atmosphere contributes to the shadow, but authored by Fred Espenak himself, The Godfather of eclipse predictions! 

This page on the eclipse, with nicely outlined parameters showed something called "Shadow Enlargement":

http://www.eclipsewise.com/lunar/LEprime/2001-2100/LE2015Apr04Tprime.html

... with a link to a clear explanation of what the Danjon shadow rule is, and its value.

It turns out that the Earth's atmosphere contributes around 1/85 (just over 1%) to the diameter of the Earth's shadow... an effect that we were NOT taking into account in Starry Night or SkySafari... but are now! (SN version 7.1.2+, SkySafari ).

Starry Night has been around for almost 20 years in some form or another, and we have never taken this into account, until now.

We could all learn a little from this power user and Keiron (and Elmo for that matter). It pays to be persistent! 

Thanks for keeping at it guys. Starry Night is that much better for it.