ABSTRACT
This chapter shows an astronomical grounding in the various objects in space and the systems. A deep sky object is a broad term referring to anything in the sky apart from singular stars and solar system objects. They form the basis of most astrophotography subjects and include nebulae, clusters and supernova remnants. A double star describes a distinguishable pair of stars that appear visually close to one another. Binary stars are one stage on, a pair of stars revolving around a common center of gravity but appear as one star. Variable stars have more scientific significance than pictorial. Supernova hunting and measuring variable stars require calibrated camera images rather than those manipulated for pictorial effect. A nebula is an interstellar cloud of dust, hydrogen, helium, oxygen, sulfur, cobalt or other ionized gas. In the beginning, before Edwin Hubble's discovery, galaxies beyond the Milky Way were called nebulae. In older texts, the Andromeda Galaxy is referred to as the Andromeda Nebula.
