Figures 6.6, 6.12cde of the hardback second edition are all flawed in that they portray a line or lines asymptotic to the steepest descent contour, and these lines are shown as passing through the origin when they should be shown passing through a point on the real p-axis given by p = 1/(alpha*sin i_s).
Ilya Tsvankin pointed this error out to me in June 2002. It was present in the first edition, went undetected for over 20 years, and was found too late to make necessary changes in the hardback version of the second edition. But it is corrected in the paperback version (April 2009).
The correction to Fig. 6.6 shown below is accurately drawn for the case where r = 5 km, |z + h| = 20 km, and alpha = 6 km/s:
Correction of part of Figure 6.6. The red curve is the steepest descent path, shown for values of X^2 (see Fig 6.12 caption) running from 0 to 50 s.
The exact path crosses the real p-axis in two places, namely where
p = sin i_s / alpha (then X^2 = 0 which is the saddle point), and where
p = 1/(alpha * sin i_s) (then X^2 = ((z + h)^2)/(r*alpha)).
The two asymptotic lines emanate from the latter point on the real p-axis. They are shown in grey.
The original Fig. 6.6 had the correct slope for these lines (slope = 0.25 in
the present case with r = 5 and |z + h| = 20), but showed the lines incorrectly
as passing through the origin, instead of through the point
p = 1/(alpha * sin i_s) on the real p-axis.