I wasn't using a tripod at the time. I had the camera set up on a surface that had a small raised lip. I used the camera's zoom ring, not the focus ring, to turn the camera while it rested on said lip. So, in essence, while I turned the zoom ring, the camera was zooming and turning at the same time. The lip kept the angle of the shot on a horizontal plane, so there weren't any ups or down at all. It was something completely random I had tried while shooting one night on the roof.
And much appreciated for the ADDS to your resource library. Always a pleasure to get the esteem of my fellow deviants, and in this case, fellow NYC'er.