Discovered by William Herschel in 1786.
Planetary nebula NGC 2438 appears superimposed over the open star cluster M46, although it is certainly not a member of the cluster, but a foreground object. NGC 2438 is one of the discoveries of William Herschel, who cataloged it as H IV.39.
In my image the faint central star can be seen close to a background star, which is probably a member of M46, as are many of the other stars in the image. The central star is of magnitude 17.5.