  Context: The morphology of massive star formation in the central regions of
galaxies is an important tracer of the dynamical processes that govern the
evolution of disk, bulge, and nuclear activity. Aims: We present optical
imaging of the central regions of a sample of 73 spiral galaxies in the H alpha
line and in optical broad bands, and derive information on the morphology of
massive star formation. Methods: We obtained images with the William Herschel
Telescope, mostly at a spatial resolution of below one second of arc. For most
galaxies, no H alpha imaging is available in the literature. We outline the
observing and data reduction procedures, list basic properties, and present the
I-band and continuum-subtracted H alpha images. We classify the morphology of
the nuclear and circumnuclear H alpha emission and explore trends with host
galaxy parameters. Results: We confirm that late-type galaxies have a patchy
circumnuclear appearance in H alpha, and that nuclear rings occur primarily in
spiral types Sa-Sbc. We identify a number of previously unknown nuclear rings,
and confirm that nuclear rings are predominantly hosted by barred galaxies.
Conclusions: Other than in stimulating nuclear rings, bars do not influence the
relative strength of the nuclear H alpha peak, nor the circumnuclear H alpha
morphology. Even though our selection criteria led to an over-abundance of
galaxies with close massive companions, we do not find any significant
influence of the presence or absence of a close companion on the relative
strength of the nuclear H alpha peak, nor on the H alpha morphology around the
nucleus.
