Some answers …

Paul Luckas

… can be found here (for anyone interested):

Schneider, S. E., Terzian, Y., Purgathofer, A., & Perinotto, M. (1983). Radial velocities of planetary nebulae. The Astrophysical Journal Supplement Series, 52, 399.

Though I thought operating at about 500 Å/mm would get me within 50 km/s, clearly there are other factors at play. Fortunately I also own a Lhires (I just need clear weather).