Abell 33
Abell 33 is a faint spherical planetary nebula located 2700 light years away in the constellation of Hydra. It lies just behind the star HD 83535 which has no relation to the nebula. The star HD 83535 is also responsible for the "diamond ring" effect seen in the photograph.
The nebula gets its coloration from the O III emissions. The nebula is faint making it difficult to be seen using a telescope. The spherical shape of Abell 33 is mainly caused by its central star not having much of a spin. The nebula shares similar morphology to another nebula with the same spherical shape, the Owl Nebula, but is much darker than the Owl Nebula.
There is also a galaxy cluster known as Abell 33, because there are two Abell astronomical catalogs, one for planetary nebulae, and one for galaxy clusters.