Photon capture cones and embedding diagrams of the Ernst spacetime

The differences between the character of the Schwarzschild and Ernst spacet imes are illustrated by comparing the photon capture cones, and the embeddi ng diagrams of the t = constant sections of the equatorial planes of both t he ordinary and optical reference geometry of these spacetimes. The non-hat asymptotic character of the Ernst spacetime reflects itself in two manifes t facts: the escape photon cones correspond to a purely outward radial dire ction, and the embedding diagrams of both the ordinary and optical geometry shrink to zero radius asymptotically. Using the properties of the embeddin g diagrams, regions of these spacetimes which could have similar character are estimated, and it is argued that they can exist for the Ernst spacetime s with a sufficiently low strength of the magnetic field.