To begin with: there are basically two types of targets in Astrophotography:
Targets within our solar system
Targets outside of our solar system (referred to as deep sky targets)
The procedure and equipment one needs to capture images depends on which type of target one is trying to image.
I pursue the path of deep sky imaging. The following images depict objects outside of our solar system (in case of galaxy photos even outside our own galaxy – the Milky Way).