Party with the stars this summer. Read SPACE.com's Special Report on summer stargazing.

On July 22, 1995 -- a warm summer night in Arizona -- a few friends have gathered in a remote location in the desert south of Phoenix, bringing along telescopes to do some stargazing in the clear, dry air.

Later in the evening they observe M 70, a star cluster that appears as a small, fuzzy ball of stars in the constellation Sagittarius. As M 70 drifts out of the field of view, one of the observers, Tom Bopp, notices that another small, fuzzy object has drifted into view. Not recognizing it, Tom and his fellow observers Jim Stevens and Kevin Gill look for it in the star charts, but find no record of such an object at that position. They decide to come back to it later.

About an hour later they check the object again and find that it has moved against the background stars. Tom Bopp races to his home outside of Phoenix and fires off a message to the Central Bureau for Astronomical Telegrams (CBAT), the clearinghouse for reporting possible astronomical discoveries. Bopp then goes to bed, but finds it difficult to get to sleep.

The next morning Daniel Green of CBAT phones Bopp and gives him the news: He has discovered a new comet, one simultaneously reported by astronomer Alan Hale of New Mexico. Over the next two years Comet Hale-Bopp becomes the comet of the century -- a huge, bright apparition that at times covers nearly half the sky and is the most viewed and photographed comet of all time.

Comet Hale-Bopp was a very unusual comet, but its discovery by an amateur is not. Even with the advent of automated search programs run by universities and large observatories, amateurs continue to report a number of the new comets each year.

And it's not just new comets:

• Robert Evans, a church pastor in New South Wales, Australia, relying only on a small telescope and a practiced eye, has made more than 35 supernova discoveries to date. That's more than any other individual -- amateur or professional.
• Paul Comba of Prescott, Arizona, working with a telescope in his backyard, has discovered more than 50 new asteroids in the last five years alone.
• Earlier this year a small team of amateur astronomers -- Frank Chalupka, Dennis Hohman, Tom Bakowski and Bill Aquino -- working near Buffalo, New York with a 40-year-old telescope and a home-built camera, took one of the earliest photos ever taken of a gamma-ray burst in a distant galaxy.

• During the Leonids meteor shower last November, Brian Cudnik of Houston, Texas and David Dunham of Greenbelt, Maryland cooperated on the first-ever-confirmed observation of a meteor strike on the moon. Cudnik is a member and Dunham is the president of the International Occultation Timing Association (IOTA), an association formed mostly of amateurs who work on high-resolution mapping of the surface contours of the moon and asteroids.
• Dr. Donald Parker of Coral Gables, Florida is a dentist by day, but at night he takes planetary photos using homemade instruments that rival, and at times exceed, the work done at many large observatories. His images are used by researchers worldwide to track weather and surface phenomena on Mars, Jupiter and other planets.

Amateurs report many of the new supernovae and new asteroids, as well as do a great bulk of the work locating returning asteroids and comets. They also have taken on a lion's share of mapping the sizes and shapes of hundreds of asteroids, as well as making very high-resolution maps of the moon's contours. Amateurs have even put in much of the basic research effort for some forms of astrophysics, such as doing most of the data collection on variable and cataclysmic stars, which has resulted in a number of advances in the theories on how stars are formed and how they work.

But astronomy is different, in part because the sky is equally available to everyone. The instruments of astronomy are also affordable to most people, and can even be homemade. (The telescope that Tom Bopp used to discover Hale-Bopp was homemade, as are many of the other instruments that reveal new discoveries each year.) These factors, along with a long tradition of amateurs and professionals working together on astronomical research and discoveries, have created an environment where any interested amateur can make significant contributions at the forefront of research, and even make new discoveries.

• The American Association of Variable Star Observers (AAVSO): coordinates amateur research programs on variable stars, gamma-ray bursts, nova and supernova searches and other transient phenomena.
• The Association of Lunar and Planetary Observers (ALPO): gathers and coordinates high-resolution observations of objects in the solar system -- including the moon, planets and asteroids.
• The International Occultation Timing Association (IOTA): runs a worldwide observing program to collect precise data on eclipses and occultations. (Occultations are eclipses of stars by objects within the solar system; these are very useful for making precise measurements of the sizes and shapes of such bodies, even tiny asteroids.)

Organizations such as this, along with reasonably priced equipment and the long tradition of amateurs working in astronomy, make it possible for anyone to take part in leading-edge research on some of the great questions of the cosmos. For those who long to take part in the adventure of discovery, astronomy therefore offers a unique opportunity -- not only for an enjoyable pursuit, but to work at the forefront of science. It's an allure that thousands of amateurs worldwide find impossible to resist.