Images of the hypersonic knotty outflow of MyCn 18. Left: a continuum subtracted image of MyCn 18 revealing the relative positions of the high-speed knots. Right: a P-V array for a long-slit placed down the nebula’s major axis and through various knots, located north and south of the nebular lobes. The slit position shown on the left is a rough estimate of that used to produce the P-V array on the right. The knots south of the nebula (and through the slit) in the continuum subtracted image present the knots in the top left of the P-V array, and conversely, the knots north of the nebula present those in the bottom right. Both images in the figure are adopted from O’Connor et al. (2000).