To get a long exposure time with the Canon Rebel XTi, you must set the camera to Bulb Mode.
Set the camera to Manual (M) mode.
Adjust the aperture (F-Stop) by turning the Scroll Wheel.
Hold the AV+- Button and turn the Scroll Wheel to Bulb Mode.
The shutter will remain open for as long as you hold the Shutter Release Button. I bought a cheap remote switch which has a lock that will hold the shutter open for as long as I need it to.
I got back home a couple nights ago from Tennessee after spending over a week and an entire cold there. Because of the constantly dripping nose, the rancid cough, and the general feeling of sick, I spent quite a bit of time at the house. One night when it was shockingly frigid for my Central Texas internal thermostat, I wandered out in a few layers of clothes (roughly 10) and took some shots of the night sky including the tree line. At least there wasn't any wind which I'm sure made the dozens of pilots thrilled whom I counted overhead while waiting for my camera's shutter.
Here's an unedited image I took:
Terrible, right? I discovered that my camera cannot take shots longer than 30 seconds. I would have preferred a full 1 minute shot for starters. Some kind of manual exposure setting. Something! There might be some trick to it, but I didn't take the manual with me and didn't have a solid internet connection or the wherewithal to bother finding one online.
After some editing in GIMP, here's the shot:
Fuzzy, grainy, and horrible despite some sense of what the shot would have been. Granted, exposures longer than 30 seconds are rare for me, but here's a case where I would have really liked a manual exposure option.
I hope everyone in the US and the ex-pats had a great Thanksgiving!