Deep Sky objects are classed as all the 'faint fuzzies' in the night sky. They include Galaxies, Nebula, Gas Clouds, and Star Clusters. These objects are mostly not very bright and require long exposures to get an image. This was a problem when using slide film to image objects, as long tacking periods were needed. With the advancement of CCD and digital imaging, things became easier as you may only need a few minutes of imaging per object comared to a few hours when using slide film.
Below are sme links to images I have taken. Some where using slide film, others were with CCD.