http://edition.cnn.com/2008/LIVING/wayoflife/06/06/ghost.hunters.ap/

Mark DeLong, left, and Jim Willis monitor paranormal activity with a computer in Urbana, Ohio. 

About 90 people tiptoed around night-vision cameras atop tiny silver tripods and dodged remote sensors connected to a computerized surveillance system. They waited for the Lincoln Ghost Train, which some people believe passes through this western Ohio city on the anniversary of the 1865 trip that carried the president's body to Springfield, Illinois, for burial.

Ghost-hunting groups around the country are swelling with members -- their popularity fueled by television shows, the Internet and the increasing availability of high-tech equipment.

"Academics pooh-pooh all of this usually," said Julieanne Phillips, an assistant professor at Urbana University who invited the ghost hunters and organized the vigil that also included about 80 students and residents. "I'm hoping for some vindication that there might be some type of paranormal activity surrounding this."

On this April night, there wasn't.

"Ghost reality shows have really opened the door for people to get involved themselves," said James Willis, founder of The Ghosts of Ohio, the group watching the tracks for the paranormal train.

The airwaves are populated with shows such as "Ghost Whisperer," "Medium," "Paranormal State" and "Ghost Hunters."

The Rhode Island-based society currently has about 80 affiliates in 44 states, twice the number of affiliates it had two years ago. And there are about 800 individual members within those affiliates, up from 300 three years ago.

"Thank God for the 'Ghost Hunters' on SCI FI," said Patti Starr, founder of the Lexington, Kentucky-based Ghost Chasers International. "Through that show, I think people see we are really serious about what we do, and they've raised the bar."

Even the U.S. Air Force has gone along, inviting "Ghost Hunters" to investigate reports of unusual occurrences at Wright-Patterson Air Force Base near Dayton. The episode showed a flashlight turning on by itself and unexplained knocks and door-closings.

Other groups are feeling the surge of interest in ghost hunting.

A Midwest Haunting, based in MaComb, Illinois, offers October tours of buildings, cemeteries and other sites it has investigated and believes to be haunted. The number of people taking the tours has tripled, jumping from about 600 in 2006 to 1,800 last year.

Forty of the 60 people who attended a recent dinner in Erie, Pennsylvania., that featured the Paranormal Study and Research Group asked if they could join the group or tag along on ghost hunts. A year earlier, only two or three asked to be involved after a similar event.

"We're actually grateful for ("Ghost Hunters") because instead of being a bunch of freaks, we're like the cool people on TV," founder Pat Jones said. "People used to look at us like we were absolutely insane, and now they want to come along with us. It's almost like every day is Halloween."

More than 500 people have registered to post and read messages and articles on the Idaho Spirit Seekers' Web site since the message board went up in November. "That really shows the interest that people do have and that it's becoming more acceptable to talk about," said executive director Marie Cuff.

Thirty-four percent of Americans say they believe in ghosts, according to a survey conducted in October by The Associated Press and Ipsos.

Joe Nickell, senior research fellow with the Amherst, New York-based Committee for Skeptical Inquiry, said he has investigated dozens of reported hauntings since 1969 and has turned up no evidence of ghosts.

Equipment being used to try to detect ghosts is not designed for that, Nickell said. Ghost hunters often arm themselves with electromagnetic detectors, thermometers that can identify cold spots and wireless microphones that eliminate background noise.

Orbs of light that show up on photos, he said, are often tiny particles of dust or moisture close to the lens of the camera, "voices" picked up by tape recorders can be radio signals or noise from the recorder, and electromagnetic detectors can be set off by faulty wiring or microwave towers.

"The least likely explanation for any given reading is it is a ghost," he said.

Willis' group, which has grown to 30 members since it was founded in 1999, includes both true believers and total skeptics.

"If you want to be taken seriously in this field, you have to acknowledge that some of the stuff out there is not real," he said. "They're looking for answers, one way or another."