I'm not that familiar with Mavicas but if you're interested in shooting video in the dark, you would probably be better off using a video camera, such as a Sony Handycam with the Nightshot feature. By using a video camera, you get longer shooting times (1 hour on a MiniDV tape), which increases the chances that you'll catch something. Then you can also use the Mavica with a flash, to try and catch orbs.
If you have to use the Mavica, see if it has a slow shutter mode when shooting MPEG. If it has an accessory shoe, you might be able to get a IR light for it, to adapt it for night vision shooting.