We present new radial velocity measurements of 586 stars in a one-degree field centered on the open cluster M46 , and the planetary nebula NGC 2438 located within a nuclear radius of the cluster .
The data are based on medium-resolution optical and near-infrared spectra taken with the AAOmega spectrograph on the Anglo-Australian Telescope .
We find a velocity difference of about 30 km s ^ { -1 } between the cluster and the nebula , thus removing all ambiguities about the cluster membership of the planetary nebula caused by contradicting results in the literature .
The line-of-sight velocity dispersion of the cluster is 3.9 \pm 0.3 km s ^ { -1 } , likely to be affected by a significant population of binary stars .