What would cause seemingly sensible teens to spend a night away from the comforts of home and sleep on a sidewalk?

The latest installment of the "Harry Potter" series, "Harry Potter and the Half-Blood Prince," premiered at midnight Tuesday at the Ashland Street Cinemas. As of 1 p.m. Tuesday, about 20 fans were camped out to secure a spot for the sixth film in the wildly popular franchise. The line was expected to get longer as the day progressed.

What would cause seemingly sensible teens to spend a night away from the comforts of home and sleep on a sidewalk? The answer can only be explained by the magic of "Harry Potter," tradition, and the vice president and director of film for Coming Attractions Theaters, Lee Fuchsmann. Coming Attractions Theaters owns the movie theater in the Ashland Plaza.

"We always get a line for it," Fuchsmann said. "It's very popular in Ashland because of the books. The only other film that inspires this is 'Star Wars.'"

Fuchsmann said the teens were camped out when she left work, at 9 p.m. Monday night.

First in the queue were Ashland residents Colette Pare-Miller, 19, and Alexandra Gurwell, 17. Their spot in line involved a little bribery, and some Potter-style partying.

"We paid some little boys to stand in line for us last night because we had a Harry Potter party," Pare-Miller said. "We got here at 10 last night and have been here ever since."

The second group skipped the night out and arrived at 8 a.m. Tuesday morning. They spared no luxury, with lawn chairs, sleeping bags, and friends stopping by with food. Some played cards while reminiscing about past Potter campouts, which Ashlander Molly Davis, 17, called "good times."

"We've been to every one," said Ami Jacobson, 17, of Ashland, sporting a big pair of spectacles without lenses. "We have been waiting for this one for a year and a half."

The girls pondered their expectations of the film and the aging of the actors, a progression that mirrors their own. The first Harry Potter, "Harry Potter and the Sorcerer's Stone," premiered in 2001.

"Well, obviously it's going to be amazing, considering the story line," said Anna Hume, 17, while eating a California roll, "but I'm a little wary about this one."

According to Hume, as Harry Potter gets older, the story lines get darker. She is worried the PG rating won't allow the movie to explore this. Hume thinks it might have been made to please the public, just to make money.

Gurwell was trying to be optimistic, knowing full well it wouldn't be as good as the book.

Ashlanders Kaitlin Megarit and Hillary Gorson, both 16, were prepared with a portable DVD player and the first five Harry Potter movies. They planned on watching them all, in order, before the big event.

The aging of the actors in the film has not affected these fans as it has drawn reactions from many movie critics. Those in line were probably the same age when the series began.

"I think it affects the movie in a good way," Pare-Miller said. "In the first one, they were so young."

On actor Daniel Radcliffe, Gorson exclaimed, "He's hot!"

The power of Potter has not faded over the years, and may get even bigger with this release.

"Advance sales on this one are better than the last one," Fuchsmann said, "so, Harry Potter is experiencing a resurgence."

According to boxofficemojo.com, the first in the series, "Harry Potter and the Sorcerer's Stone," holds the Potter box-office record, earning over $317.5 million. "The Half-Blood Prince" is expected to hold its own.

"It'll take the weekend and the month," Fuchsmann said. "It'll probably take the year also."

This is not the last for fans of Harry Potter. Warner Brothers plans on releasing the seventh film, "Harry Potter and the Deathly Hallows," in 2010.