Hubble Telescope turns 20! Here's 10 space targets you can spot without the Hubble.

Of all the countless great and wonderful objects that have been imaged by the Hubble Space Telescope during its first 20 years of operation, we thought it might be interesting to find some Hubble objects that can be seen from Earth – either with the unaided eye or employing a small telescope.

The outstanding capabilities of the Hubble Space Telescope, which launched April 24, 1990 on the space shuttle Discovery, have enabled us to see these objects more clearly than any ground-based instrument. And in the first two cases, we were afforded close-up views of what could only be termed as very unusual, if not rare events. Here's a look at Hubble targets amateur astronomers can hunt for too:

Saturn's Great White Spot

In its very first year of operation, the Hubble captured an exceedingly rare event: A major storm on Saturn, dubbed, the Great White Spot. It turned out to be a fantastic system of swirling clouds and eddies. The image was taken on Nov. 9, 1990 and depicts what may arguably have been the greatest atmospheric feature in the solar system.

IN PICTURES: Images from the Hubble Telescope

Nobody had dreamed that they would see anything as spectacular as what appeared on NASA's television monitors when the first images of the storm from Hubble began arriving. After computer processing to remove the blurring effects of its flawed primary mirror, the images revealed a white-spot disturbance 200,000 miles long and 6,000 miles wide.

"I came apart at the seams," said James A. Westphal, who was then principal investigator for HST's wide-field and planetary camera. "My colleagues ribbed me, saying 'Westphal, that's Jupiter and you've put rings around it."

How to find Saturn: This week, at darkness falls at around 9:00 p.m. local daylight time you can find Saturn about halfway up in the southeast sky and positioned roughly midway between the 1st-magnitude stars Regulus in Leo and Spica in Virgo. Saturn, shining with a sedate yellowish-white glow at magnitude +0.7, is brighter than either of these stars.

It will be due south at around 10:30 p.m. and doesn't set in the west until after 4:30 a.m. The rings are visible with a telescope magnifying at least 30-power and they are currently tipped only about 2-degrees to our line of sight.

Jupiter's comet crash

The planet Jupiter made headlines again in mid-July 2009 when a dark "blemish" near Jupiter's south pole was sighted by Australian amateur astronomer Anthony Wesley from his backyard observatory. Slowly, as Jupiter's rotation turned the blemish toward Earth, Wesley got a better view of it and he realized that what he was looking at was a Jupiter comet impact.

Soon, observers from around the world confirmed Wesley's observation and proved a tempting enough target for scientists to put a hold on testing out the revamped Hubble Space Telescope and use its newly installed WFC-3 camera to capture an image of the rare event. The Hubble image shows lumpiness to the debris plume caused by turbulence in Jupiter's atmosphere.

"It was important for Hubble to get an early look," said Hubble spokesman Ray Villard.

How to find Jupiter: This week it shines low in the east-southeast as morning twilight strengthens. At magnitude -2.1, it's unmistakable, shining with a brilliant silver-white luster. By the last week of May Jupiter should provide a fairly good telescopic view, being at least 20-degrees up in the southeast during morning twilight (for observers at mid-northern latitudes). By later this summer it will be in fine position for observation for most of the night.

Andromeda Galaxy's double center

The Andromeda Galaxy is dimly visible to the unaided eye as an elongated patch of hazy light. At a distance of 2.5 million light years, it is one of the farthest objects visible to the naked eye, and can be seen even from urban areas with binoculars.

In 1991 astronomer, Tod R. Lauer used the Wide Field and Planetary Camera (WFPC), then onboard the Hubble Space Telescope, to image Andromeda's inner nucleus. The nucleus was found to be double, consisting of two concentrations separated by nearly 5 light years. The brighter concentration is offset from the center of the galaxy.

The dimmer concentration, falls at the true center of the galaxy. Canadian astrophysicist Scott Tremaine has proposed that the double nucleus is the result of the brighter concentration representing the projection of a disk of stars in an eccentric orbit around a black hole at the galaxy's central core.

How to find the Andromeda Galaxy: This week, the Galaxy is visible in the predawn sky low in the northeast. If you don't care to arise so early you'll have a good view of Andromeda during evening hours from the end of July to mid March. First locate the Great Square of Pegasus, focusing binoculars on the star in the upper left corner of the Square (Alpheratz). Run straight across and get the star Mirach in your field of view. Then run slowly "up" to a fairly bright star above Mirach. Just above that star you'll see a hazy patch of light.

That's the Andromeda Galaxy.

Mars: Up close and personal

Because Earth and Mars follow elliptical orbits around the sun, Mars's closest approach to Earth usually occurs several days before or after opposition – when it appears directly opposite to the Sun. On Aug. 27, 2003, at 5:51 a.m. EDT, Mars came within 34,646,420 miles (55,757,930 km) of Earth at 5:51 a.m., which is just about as close as it can possibly come. At that moment, the Earth-Mars distance was the smallest in nearly 60,000 years. It would have taken a light beam 3 minutes and 6 seconds to cross the interplanetary gulf between Earth and Mars. Opposition came the following day. The next opposition bringing Mars even closer will not occur until Aug. 29, 2287. This image was made within minutes of the closest approach.

How to find Mars: Now well up in the southern sky at dusk; Mars sets between midnight and dawn. As Mars recedes from the Earth, it continues to diminish in brightness. Currently it's a fading golden-orange ember at magnitude +0.7. During the latter part of May it forms an increasingly eye-catching pattern with the nearby bright stars of Leo's star-shaggy head and chest. In fact, Mars will team up with the bluish 1st-magnitude star Regulus for a strikingly close conjunction on June 7.

The Great Orion Nebula

Within the brilliant constellation of Orion, the Hunter is a stellar incubator: The Great Orion Nebula. A sort of auroral glow is induced in this nebula by fluorescence from the strong ultraviolet radiation of four hot stars entangled within it.

The Great Orion Nebula is a vast cloud of extremely tenuous glowing gas and dust, approximately 1,600 light years away and about 30 light years across (or more than 20,000 times the diameter of the entire Solar System). Astrophysicists now believe that this nebulous stuff is a stellar incubator; the primeval chaos from which star formation is presently underway.

How to find the Orion Nebula: You'll have to look quick this week, for Orion – primarily a winter constellation – is now dropping rapidly down into the western sky at dusk. Once you locate his familiar three star belt look immediately below the belt for a fainter trio which marks Orion's sword. It appears to surround the middle star of the three. To the naked eye it appears not as a point of light like a star, but as a diffuse spot that is dim, but unmistakable. It is resolved in good binoculars and small telescopes as a bright gray-green mist enveloping the star. In larger telescopes it appears as a great glowing irregular cloud.

The Crab Nebula

This was the first item on Charles Messier's list of fuzzy objects. Messier was an 18th century comet hunter who compiled a list of nuisances that he did not want to confuse with comets. M1 (for Messier 1) in Taurus has been taken for a comet by others using small telescopes, but we know it as the Crab Nebula.

This cloud began its existence in a tremendous explosion recorded by observers in the Orient and our Desert Southwest on July 4, 1054. Although it's 6,500 light-years away, this dazzling supernova was visible in the daytime for weeks, and at night for two years. The gas cloud, now called a supernova remnant, is still expanding and emits radio waves as well as light.

How to find the Crab Nebula: It is located between the two stars marking the tips of the horns of Taurus, the bull. A word of caution: you should have access to a dark, clear sky, for at magnitude +8.4, the Crab unfortunately has a tendency to get lost in the background illumination in light polluted locations. It may be just barely visible as a dim patch of light in good binoculars.

It is more readily detectable in a 3-inch telescope and begins to appear as irregularly oval-shaped with telescopes of 6-inch aperture or greater. Unfortunately, Taurus is now quite low in the west-northwest right after sunset and will soon disappear from our evening sky. It will begin to reappear low in east-northeast before sunrise in July; by September Taurus is nearly overhead at dawn and will be readily visible during convenient evening hours during the fall and winter months.

Core of Hercules's Great Globular Cluster

A collection of stars numbering over 100,000, it is one of the brightest globular star clusters in the northern sky. At a distance of 25,000 light-years, and over 12 billion years old, the cluster's stars crowd into a region 150 light-years in diameter. Near the core of this cluster, the density of stars is about a hundred times greater than the density in the neighborhood of our sun.

How to find the Great Cluster? The rather dim constellation of Hercules is low in the northeast sky at dusk, but stands almost directly overhead by around 4 a.m. Look toward the four stars, known as the "Keystone" which supposedly forms the body of Hercules.

A keystone is the stone atop an arch, and has this shape, narrower at one end. It's between the two western stars of the keystone that we can find the Great Globular Cluster of Hercules. It's about a third of the way along a line drawn from the stars Eta to Zeta. Edmund Halley (of comet fame), first mentioned it in 1715, having discovered it the previous year: "This is but a little Patch," he wrote, "but it shows itself to the naked eye, when the sky is serene and the Moon absent."

Sagittarius Star Cloud

Never visible from large cities with their lights, smoke and haze, the beautiful Milky Way can still be readily viewed from distant suburbs and rural locations. Before the invention of the telescope, the true nature of the Milky Way Galaxy ("Gala" is Greek for milk) was a mystery.

Binoculars and telescopes reveal that the galaxy consists of dense clouds of individual stars. For observers in the Northern Hemisphere, the brightest part of the Milky Way is in the constellation Sagittarius, near the star El Nasl. Astronomers believe that this region marks the "hub" or central condensation of our own galaxy.

The Sagittarius Star Cloud, about 30,000 light-years distant, seems to be the nucleus, with the sun and all the outer stars of the outer stars of the galaxy turning at the rate of 155 miles per second and apparently requiring 200 million of our Earthly years to make one complete revolution, or one "cosmic year."

How to find the Sagittarius Star Cloud: Sagittarius, which depending on how you look at it, resembles either a Teapot or an upturned dipper, used presumably to dip up the Milky Way. In late April, Sagittarius can be found low in the southeast around 3 or 4 a.m. local time. By dawn it is nearly due south. Sagittarius is primarily a summer star pattern, which is when you can also find it in the southern sky before midnight during July and August.

The Ring Nebula

The Ring Nebula is the most famous and among the brightest examples of what astronomers refer to as "planetary" nebulae. It's likely a ring of bright material surrounding its central star. It is generally believed that sometime in the distant past, a star nearing the end of its life and having used up all of its nuclear fuel hurled great masses of gas out into space in a gaseous shell.

This surrounding gas is still expanding and is made visible by the illumination from its extremely hot central star (which is merely the core left from the original star). The surface temperature of the star has been estimated at 216,000-degrees F (120,000-degrees C). Our own sun is expected to undergo a similar process in a few billion years.

How to find the Ring Nebula: It's located in the small constellation of Lyra, the lyre, which this week is low in the northeast sky before midnight and is practically overhead at dawn. The ring can be located between the stars Sheliak and Gamma and shines at magnitude +8.8, and thus is far too faint to be seen with the unaided eye.

Any good pair of binoculars will locate it, though the ring shape only becomes clearly evident to most eyes using a 6-inch telescope. With larger instruments and higher magnifications, the ring appears distinctly as a "tiny ghostly doughnut."

Dwarf Planet Ceres

Ceres is the smallest identified dwarf planet in the Solar System and the only one in the asteroid belt. It was discovered on Jan. 1 1801, by Giuseppe Piazzi and for half a century it was classified as the eighth planet.

With a diameter of about 590 mi (950 km), Ceres is by far the largest and most massive body in the asteroid belt, and contains almost a third of the belt's total mass. Hubble photographed Ceres over a 2-hour and 20-minute span, the time it takes the Texas-sized object to complete one quarter of a rotation. One day on Ceres lasts 9 hours. Hubble snapped 267 images of Ceres from Dec. 2003 through Jan. 2004 as it made more than one rotation.

Astronomers confirmed that Ceres has a nearly round body like Earth's. Ceres' shape suggests that its interior is layered like those of terrestrial planets such as Earth, and may have a rocky inner core, an icy mantle, and a thin, dusty outer crust inferred from its density and rotation rate. The bright spot that appears in each image is a mystery. It is brighter than its surroundings. Yet it is still very dark, reflecting only a small portion of the sunlight that shines on it.

How to spot Ceres: Barely beyond the threshold of naked eye visibility, it can be seen with good binoculars or a small telescope. For the next few months we must search for it amid a rich background of the star clouds, clusters, and nebulae of the Sagittarius Milky Way. Around June 1, Ceres will appear to traverse the famous Lagoon Nebula. It will arrive at opposition on Jun. 18, shining like a 7th magnitude star at a distance of 69 million mi (274 million km).

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IN PICTURES: Images from the Hubble Telescope

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.