When darkness comes, another world beckons, luring Mazlin down a curving staircase into the basement of his palatial Upper Makefield home and out to his one-acre backyard, where he begins the night's work.

A board-certified neurologist in Langhorne, Mazlin is a self-described astrophotographer, one of maybe 100 in the country, 200 or so in the world. They can produce stunning images, not merely of the moon and planets but also of nebulae (interstellar cloud masses of dust and gas) and distant galaxies with their magical clusters of stars.

The pictures he produces of the Whirlpool Galaxy or the Orion Belt and Sword Mosaic - two of his favorites - are dazzling, a panoply of startling colors and exotic shapes. They hang throughout his house and are given to fortunate friends or donated to schools as fund-raisers. From time to time, a patient or a visitor to his Web site - fourthdimensionastroimaging.com - will buy one.

This month marks the start of "sky high" season for Mazlin. The first in a series of meteor showers - Orionids from the constellation Orin - is expected just before dawn Oct. 21; Leonids, from the constellation Leo, may be visible in the early hours of Nov. 17-18; and Geminids, from the constellation Gemini, will streak across the sky Dec. 13-14.

Later this month, Mazlin will get a head start in commemorating 2009 as the International Year of Astronomy, marking the 400th anniversary of Galileo's first astronomical observation through a telescope. He will spend a week in Chile, where in a mountaintop observatory, he will begin imaging celestial targets visible only in the Southern Hemisphere.

Mazlin, 49, became hooked on astronomy when he was a teenager on Long Island and a friend with a telescope gave him his first glimpse of Saturn. "You see all those rings around the planet, and it takes your breath away," he recalls. "I remember thinking, 'One day I'll get into it.' "

That day didn't come until 15 years ago, when Mazlin was thumbing through "one of those "yuppie catalogs," saw an advertisement for an entry-level telescope, and thought, "Why not now?"

"At first, we would simply lie out back on our lounge chairs with the telescope and try to find where the different stars were," remembers his wife, Violet. "But before long Steve's knowledge and passion far surpassed mine, and he left me in the cosmic dust."

Ten years ago, the convergence of high-tech computers, sophisticated telescopes, and digital cameras with their high resolution and sensitivity to light allowed Mazlin to begin realizing his childhood dream - making detailed pictures of the wonders in the sky.

Mazlin has never taken an astronomy, photography or computer course. He didn't own a computer or see any need to have one until 1996, when he saw the possibilities of using it for imaging deep into the sky.

"With what is available today, anyone can do it," he says, "provided you're willing to invest the time and the money, roughly $3,000 to $5,000 for the basic equipment." After purchasing the setup - a telescope, a digital camera with an interchangeable lens that can hook up to it, a mount that moves the telescope across the sky, and a laptop or desktop computer equipped with a planetarium program, such as The Sky and Adobe Photoshop for processing - maintenance is minimal.

But the serious stargazer, like Mazlin, will soon want to add the bells and whistles that will up the ante and the satisfaction.

In the beginning, Mazlin would stay outdoors in his dome observatory, 100 feet from his house, until two or three in the morning, covered by protective mosquito netting in the summer or a bulky parka and knee-length boots in the winter, trying not to be spooked by the flying bats and the insects buzzing in his ear as he adjusted the settings on his telescope and painstakingly rotated the dome by hand to get multiple exposures throughout the night.

Today, with an investment of more than $50,000 - including a telescope bought from John Stiles of Huntingdon Valley, who has been building them for 20 years in the basement of his family-owned funeral parlor - he spends only five to 30 minutes doing the same thing.

Mazlin works in the same white fiberglass observatory, named "My Hy" in honor of his parents, Myra and Hyman. But its dome rotates automatically now, sparing Mazlin his nighttime vigil.

To shoot a distant galaxy, the mount must move at precisely the same speed as the Earth is rotating and follow it across the sky. The chips in his camera - a guide chip and an imaging chip - make it possible for him to do that.

Much of the work happens without him. A computer in his home collects the data that accumulate all night, recording the intricate detail and stunning colors that the human eye has limited ability to see even through a telescope. "I sleep through it," Mazlin confesses.

That's the easy part. Processing the data can take weeks. Each of Mazlin's exposures, taken through different filters, covers anywhere from five to 30 minutes. Working with Adobe Photoshop, he removes the effects of thermally generated noise and digitally superimposes his images into one that may represent 31 hours of photography.

One of his photographs shows two galaxies colliding. Another looks like the interior of a person's brain. Sometimes he creates a mosaic, seamlessly meshing images that are impossible to picture in one field. The resulting image can consume close to a gigabyte of memory. Mazlin takes no chances. Everything is backed up multiple times on an external hard drive and on several Internet sites.

Time and inexhaustible patience are the ingredients needed to achieve Mazlin's level of expertise. He emphasizes that it's scrupulous but thrilling work from the start - a meticulous mix of art and science.

"It's up there in the sky," he says, "but in order to get it you have to navigate through tons of software and hardware gremlins that will derail you at any given time. You'll have to endure a long string of failures before you produce an image you'll be proud of. A therapeutic dose of obsessive-compulsive genes helps."

Mazlin's ultimate goal is to see a total solar eclipse. Those who have seen one liken it to an almost religious experience.

In preparation, the sky darkens, the winds pick up, and stars appear even in daylight. In ancient times, people and even animals were spooked. Today, cruise and airline trips cater to "eclipse chasers" who pursue eclipses around the world.

The next one will be in Nepal on July 22, 2009. Mazlin hopes to be there.