Buying Your First Scope

Buying Your First Scope

A telescope need not have high magnifying power or be expensive to allow you to see every planet in the solar system. It is the size of the lens aperture and the instrument’s portability that count. John Shibley, an editor at Astronomy magazine and author that publication’s annual telescope buyer’s guide, has these tips on equipping yourself to scan the heavens:

Focus on a telescope’s lens size: A lot of people ask, “What power is that scope?” Actually, magnification is irrelevant. What matters is the amount of light a telescope gathers, which depends on the size of the mirror that brings light to a focus or the size of the lens itself. The bigger the mirror or the lens, the fainter the objects you will be able to see and the better the resolution. If you don’t have a large aperture, you crank up the magnification and it just ends up stretching an image that is not any good to begin with.

Image: Elena

Start with a reflecting scope: There are two types of telescopes: reflecting and refracting. A reflecting telescope costs about half as much as a comparable-sized refracting telescope – it is excellent for star and nebulae observations and for use in astrophotography. The refracting telescope tends to distort images less and is good for lunar and solar observation. It can distort color, though, and can be difficult to move, which may turn off beginners.

Know your mounts: A scope in the $800-$1000 range has a Dobsonian mount, which means the scope can be pivoted up and down and left and right but can’t be calibrated to line up with the earth’s axis so that it automatically follows the stars. More expensive scopes come with equatorial mounts – they are the ones that actually track the sky.

Get several eyepieces: Usually you want to get three eyepieces. That is because observing the moon requires a low magnification, planets a medium magnification, and the stars a high magnification. Any eyepiece with a focal length in the upper 20s to lower 30s in millimeters is considered low-powered; from the mid-teens to the lower 20s is medium-powered. Anything lower than 12 mm is high-powered. Having more than one eyepiece allows you to adjust to atmospheric changes that may make objects look blurry.

Star Gazer’s Guide

Star Gazer’s Guide

Stars and Constellations

The Explosion that created the Universe gave birth to trillions of stars, but only 5,000 are visible to the naked eye.

Since only half the sky can be seen at any one time, that means only 2,500 stars will be in your field of vision on the next clear night. Constellations are groups of stars whose patterns remind stargazers of familiar shapes.

Le Soleil couchant. Photo by Elena

Today, astronomers recognize 88 such patterns. Their names and meanings :

Andromeda – Chained Maiden

Antila – Air Pump

Apus – Bird of Paradise

Aquarius – Water Bearer

Aquila – Eagle

Ara – Altar

Aries – Ram

Auriga - Charioteer

Bootes – Herdsman

Caelum – Chisel

Camelopardalis – Giraffe

Cancer – Crab Canes

Venatici – Hunting Dogs

Canis Major – Great Dog

Canis Minor – Little Dog

Capricornius – Sea-goat

Carina – Keel

Cassiopeia – Queen

Centaurus – Centaur

Cepheus – King

Cetus – Whale

Chamaeleon – Chameleon

Circinus – Compasses (art)

Columba – Dove

Coma Berences – Bernice’s Hair

Corona Australis – Southern Crown

Corona Borealis – Northern Crown

Corvus – Crow

Crater – Cup

Crux – Cross (Southern)

Cygnus – Swan

Delphinus – Dolphin

Dorado – Goldfish

Draco – Dragon

Equuieus – Little Horse

Eridanus – River

Fomax – Furnace

Gemini – Twins

Grus – Crane (bird)

Hercules – Hercules

Horologium – Clock

Hydra – Water Snake (female)

Hydrus – Water Snake (male)

Indus – Indian

Lacerta – Lizard

Leo – Lion

Leo Minor – Little Lion

Lepus – Hare

Libra – Balance

Lupus – Wolf

Lynx – Lynx

Lyra – Lyre

Mensa – Table Mountain

Microscopium – Microscope

Monoceros – Unicorn

Musca – Fly

Norma – Square (rule)

Octans – Octant

Ophiuchus – Serpent Bearer

Orion – Hunter

Pavo – Peacock

Pegasus – Flying Horse

Perseus – Hero

Phoenix – Phoenix

Pictor – Painter

Pisces – Fishes

Piscis Austrinius – Southern Fish

Puppis – Stern (deck)

Pyxis – Compass (sea)

Reticulum – Reticle

Sagitta – Arrow

Saggitarius – Archer

Scorpius – Scorpion

Sculptor – Sculptor

Scutum – Shield

Serpens – Serpent

Sextans – Sextants

Taurus – Bull

Telescopium – Telescope

Triangulum – Triangle

Triangulum Australe – Southern Triangle

Tucana – Toucan

Ursa Major – Great Bear

Ursa Minor – Little Bear

Vela – Sail

Virgo – Maiden

Volans – Flying Fish

Vulpecula – Fox.

Planets of the Solar System

Planets of the Solar System

There are eight planets in the solar system, including Earth, but only four besides our own are visible to the naked eye: Venus, Mars, Jupiter, and Saturn. Mercury: The smallest of the planets is Mercury. Its diameter is less than half the earth’s.

Named for the god of the winged messenger, it is the planet closes to the sun and has no satellites. It has been believed for longtime that Mercury always turned the same side toward the sun and that the sunlit part of Mercury had a temperature hotter than 600 degrees Fahrenheit. By contrast, the temperature on the side away from the sun is thought to be -460 degrees Fahrenheit. Venus: Named for the goddess of love and beauty, Venus is almost the same size as Earth and is often called Earth’s “sister planet”.

The brightest of all planets, Venus is shadowed only by the Sun and the moon. It is the first “star” to appear in the evening sky and the last to disappear in the morning. At its brightest, Venus may even be visible during the day. Many astronomers believe that the core of Venus is largely metallic, mostly made of iron and nickel. Because of the dense carbon dioxide clouds enveloping the planet, the surface of Venus can’t be seen. Earth: Ours is the third closest planet to the sun – they are only 93 million miles apart.

Seen from space, the planet appears as a blue ocean sphere with brown and green areas marking the location of its continents. Its diameter at the equator is 7,900 miles, and its atmosphere contains 78 percent nitrogen and 21 percent oxygen, in addition to traces of water in gaseous form, carbon dioxide and other gases. By measuring the radioactive decay of elements in the Earths’ crust, scientists estimate that the planet is about 4.5 billion years old. Mars: Like Earth, Mars has four seasons, but the diameter of Mars is just a little more than half that of Earth’s, and its mass is only about a tenth of ours. Named for the god of war, Mars takes 687 days to complete one revolution of the sun.

About 80 percent of the planet is carbon dioxide. The white caps that cover its poles increase in size during the Martian winter and shrink during the summer. Martian seasons are about twice as long as Earth’s. Jupiter: Next to the sun, Jupiter is the largest and most massive object in the solar system. Named for the leader of the gods, Jupiter has a mass more than twice that of all other planets combined. A body on the surface of Jupiter would weigh 2,64 times what it would weigh on Earth. Jupiter completes a revolution every 10 hours, giving it the shortest day in the solar system. It also has 12 satellites, the largest number of any planet in the solar system.

It is perhaps most famous for its Great Red Spot, which scientists believe is a storm that has been going on for more than 300 years. Saturn: The second largest planet in the solar system, Saturn is named for Titan, the father of Jupiter and the god of sowing. It is best known for its system of concentric rings, which are not visible to the naked eye. The rings are probably composed of debris from a shattered satellite. Saturn is the least dense of all the planets but one of the brightest. Uranus: Visible by the naked eye on a dark, clear night, Uranus is unique because its axis of rotation lies almost in the plane of its orbit. The planet was discovered by the German-English astronomer William Herschel in 1781. Herschel proposed to name the planet Georgium Sidus, in honor of England’s King George III. But in keeping with the tradition of naming planets after Greek gods, it was eventually named after the father of Titan and the grandfather of Jupiter

. Uranus has five known satellites and a mass over 14 times that of Earth’s. Its temperature is thought to be below -300 degrees Fahrenheit. Neptune: Named for the god of the sea, Neptune requires 165 years to complete one revolution of the sun. Its atmosphere is made of methane, hydrogen, ammonia, and helium, and its mass is about 17 times that of Earth. The planet was discovered as a result of a mathematical prediction. Two mathematicians, John Couch Adams and Urbain Le Verrier, calculated that there must be an unknown planet more distant from the sun than Uranus because they could detect the gravitational pull on Uranus.

Pluto : (this planet used to be the 9th planet, but it is now seen as a big asteroid). There is probably little or no atmosphere on Pluto because of its extreme temperature, which is nearly -400 degrees Fahrenheit. From Pluto the sun would only appear as a bright star. While it was named for the odd of the underworld, the planet’s first two letters are also the initials of Percival Lowell, whose research on gravitational forces led him to predict the planet’s existence around the beginning of 20th century. It wasn’t until after Lowell’s death, however that the planet was discovered.

Moonlight Sonata

Moonlight Sonata

Mountains on the Moon

The man in the moon is actually a series of frozen lava fields. The moon is Earth’s only natural satellite and was probably created in the same cosmic event that created the Earth.

It is only 238,860 miles away, making it an object of endless human fascination – and superstition – for millennia. Although its only light is reflected from the sun, it is the brightest object in our night-time sky. In size it is slightly more than a quarter the diameter of the Earth.

Temperatures can be as high as 273 degrees Fahrenheit on the bright side and as low as -274 degrees Fahrenheit on the dark side. There is no air, and thus no liquid water, on the lunar surface. That means the moon has no clouds, winds, rain or snow. Without air and water to cause erosion, the moon’s features are nearly permanent – they include towering mountain ranges and seas of hardened lava.

The astronomer Galileo was the first to study many of these features with the telescope he built in the early 1600s.

The moon’s laval fields are called maria, after the Latin word mare for sea, because in Galileo’s time it was thought that these plains might in fact be oceans, and that there might be life on the moon. The maria look dark from Earth, suggesting to those with a vivid imagination that there is a “a man in the moon”.

The lunar surface has also been pitted with craters from crashing meteorites – over 30,000 can be seen from Earth. The circular depressions range in size from less than a mile to over 100 miles across.

As intriguing as all of these features are, however, none of them can compare with the fact that the pull of the moon’s gravity on the earth’s oceans plays a huge role in creating our daily tides.

The Phases of the Moon

The moon takes slightly longer than 27 days to complete its elliptical orbit around the earth, but because the earth also moves around the sun, it takes 29 days, 12 hours, 44 minutes and 3 seconds to go from one new moon to the next. At the start of each orbit, the moon is directly between the earth and the sun, making the moon invisible because its dark side is toward us.

Gradually, a crescent appears and the moon passes through a waxing phase, in which it grows progressively more visible until it becomes full, and then a waning phase, in which its shape gradually shrinks to invisible again before repeating the cycle.

The Moon has no light of its own : it merely reflects the light of the sun. If the moon did not rotate as it revolves around the earth, we would see all its sides; as it is, we always see the same side. Illustration: Moving beyond the Big Dipper.

If you are curious about what beside the North Star and the Big and Little Dippers are visible in the firmament tonight, don’t rush off to the book-store just yet; sorting through the hundreds of star-gazing guides that fill the racks could leave you more confused than you were to to begin.

Beachgoer's Guide to Tides

A Beachgoer’s Guide to Tides

Skim this to know more about tidal effects than most fishermen Some ancient myth-makers held that the earth’s pulse or breathing caused the tides. The Greeks began to notice the moon’s influence when they began venturing out of the relatively tideless Mediterranean. Our modern understanding of tides is based on Sir Isaac Newton’s equilibrium theory of tides, which described the gravitational attractions of the sun and moon on the earth’s waters.

Today, tides can be predicted with astronomical precision and need no longer be a mystery. Here’s what landlubbers will fin when they are at the beach.

If you live on the East Coast, expect the tides to be semidiurnal: That’s when high and low tides occur twice per lunar day, and the heights of both the first and second set of tides are roughly the same.

A lunar day is 50 minutes longer than a day on Planet Earth, which is why in many places high and low tides occur about 50 minutes later than the corresponding tides of the previous day.

If you live on the West Coast, expect mixed tides: The tides on America’s left coast rise and fall twice per lunar day, but the heights or the second set of tides differ from the first. The different tides each day are termed higher high water, lower high water, higher low water, and lower low water. Their order of occurrence varies over the course of the moon and from place to place.

Along the Gulf of Mexico, the tides are diurnal: Here, high and low tides appear only once every day. About twice a month, near the time of the new and full moon, the tidal range between high and low tides is usually 20 percent above average. These tides, known as spring tides, occur when the sun and moon are in a straight line with the earth. When the sun and moon are at right angles to each other with respect to the earth, tidal ranges between high and low tides are about 20 percent less than average. These tides, known as neap tides, occur around the time of the first and third quarters of the moon.

For another big swing in height between high and low tide, wait until the moon is at perigee: That’s when the moon is at its closest point to the earth each month and is when the tidal range between high and low tide is greatest. Roughly two weeks later the moon is at apogee, which is its farthest point from the earth for the month. That’s when the moon’s influence is at a minimum. During the course of the month, daily inequalities between successive high or low tided also can occur: This happens as the moon moves from about 28 degrees north of the equator to 28 degrees south. When the moon is at one of these extremes, the difference in height between morning and evening tides is greatest. When the moon is at the equator, tides are roughly equal.

The tidal range also increases in January: That’s when the earth’s elliptical orbit around the sun brings the planet closest to the sun, in what astronomers call the state of perihelion. In July, when the earth is farthest away from the sun in what astronomers refer to as the state of aphelion, the tidal range decreases. The shape and depth of ocean basins change tidal ranges, too: The smallest differences in the heights between high and low tides occur along ocean coasts. For example, spring tidal ranges (near the time of the new and full moon) vary from about 2 feet on the Gulf Coast to as much as 8 or 9 feet on the California Coast.

The largest tidal ranges are found in tidal inlets, estuaries, and salt marshes. The Bay of Fundy in Canada has the greatest difference in the world between high and low tide. There, the funnel-like opening of the bay concentrates the energy and increases the height of the incoming tide, resulting in average tidal ranges of about 45 feet. Meteorological conditions can also disrupt normal tide patterns: While tide tables provide accurate times and heights of high and low tide, strong and persistent winds and the low atmospheric pressure associated with storm systems can alter the time and height of high or low tide.

If you are planning to go clamming or to collect seashells at low tide and there is a strong onshore breeze, you may want to delay for as long as an hour after the predicted time of low tide. Horizontal water movements, known as tidal currents, are generally strongest midway between high and low tide: When the tide rises and water flows in to fill estuaries and inlets, the water is called a flood current. When the tide goes out and water drains from these coastal areas, the flow is called an ebb current. Slack currents are found around the time of both high and low tide.

Surf fishing is best done when tidal currents are strongest: Strong flood currents force bait fish up closer to the beach and cause from to school up tighter and hide behind features such as rocks or jetties. Game fish such as bluefish or striped bass take advantage of these conditions, and so should knowledgeable surf fishermen, advises marine fisheries biologist Gregg Skomal. Game fish lie in wait for the bait fish to be swept in and out of inlets, estuaries, and bays by flood and ebb currents. Slack water is usually the worst time to fish. Boaters shouldn’t rely on the tidal charts in coastal newspapers. While most coastal newspapers list the times and heights of high and low tide, boaters need more tidal information than the newspapers provide in order to ensurer safe passage over the ocean floor and to know here to anchor. They should consult the tide and tidal current tables published each year by the government.

The Moon and Tides

The tide is the rise and fall of water throughout the earth’s oceans. Every 12 hours and 26 minutes, tides are created primarily by the moon’s pull of gravity on the water. When the earth is nearer the moon, water is pulled toward the moon, producing a high tide. This happens on the opposite side of the earth at the same time. Spring tides occur when the sun and the moon are directly in line. The moon is either in front of or behind the earth. This produces a very high tide twice a month. Neap tides do not rise as high as normal because the moon is at right angles to the sun. A neap tide occurs twice a month.

Safety for Swimmers and Surfers

Lifeguards recommend swimming off sheltered beaches such as those found in coves or behind a point or peninsula. Swimming is easiest out beyond the breakwaters and away from where the biggest sets of waves are breaking. Eyeball how longshore currents are flowing by watching floating debris or swimmers, and swim with the current to limit fatigue and frustration.

Many years ago Karl Tallman, a lifeguard for the California Department of Parks and Recreation gave these additional tips:

• Spilling breakers provide body or board surfers with the longest ride. Such waves commonly occur on relatively flat beaches and are characterized by foam and bubbles that spill down the front of the wave.
• Plunging breakers can break with great force right on top of an unsuspecting surf swimmer. They are found on moderately steep beaches. The crests of these waves curl over a pocket of air and result in splash-up. As waves, they are short-lived and are not the best for surfing.
• Surging breakers slide up and down the beach creating very low challenges for the surf swimmer. They occur on steep beaches and produce little or no bubbles.
• Rip currents can endanger even the most experienced swimmer. Remember to swim parallel to the shore to escape the current or allow it to carry you out to where its strength diminishes.

Expert choice: To obtain the tide and tidal current tables for your coastal region, contact National Oceanic and Atmospheric Administration Distribution Branch.