Light Pollution
Light Pollution has become a serious issue for astro photographers. 80% of the world population is living under Light Polluted skies! Under city night skies you hardly can see any stars and this will make finding and framing of your Deep Sky Objects very diffilcult. Trial by error and extremely time consuming, which will cause much frustration , with the result you loose valuable imaging time.
Long Focal Lengths
Focal Lengths > 400mm will narrow your field of view substantially and your hit rate of your targeted Deep Sky Objects will drop significantly. When targeting Deep Sky Objects who are near Zenith, finding and framing will get a tedious and difficult exercise. It can get extremely time consuming and you are losing valuable imaging time.
Orientation
Popular targets like M42 (Orion), M31 (Andromeda) or M45 (Pleiades) can be found easily, but other targets are more difficult to find depending on the Bortle Class your are imaging in. Questions like - Where is IC415, NGC2237, M13, M3, Sh2-155 or NGC1499 are common and not easy to find in the Night Sky. A good orientation in the night sky is necessary to find your Deep Sky Objects with precision.
Star hopping
Under Dark Skies Star Hopping is a good method to locate your Deep Sky Objects. However, framing after you have found it can be a tedious process, depending on the focal length and position of your object in the Night Sky. Under Light Polluted skies, Star Hopping is nearly impossible.
Time Consuming
Especially when the Objects are dimmer, not easy to locate or are near zenith. When you are not able to find your Deep Sky target, frustration will become your biggest enemy (spending hours on finding and framing up your target are not seldom) and many may stop their Astro Photography journey before they even have started, although they still dream from those wonderful Night Sky Objects.
