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The term "deep sky" applies to objects visible from Earth that are outside the solar system. As these are normally much fainter than the brighter solar system objects and many of them are large, with their brightness spread out over a large area, you normally need clearer skies and larger instruments to enjoy them. Indeed, living in the south west of England, I can usually count 10-15 exceptionally clear nights. On such nights, there's nothing better than just looking around with a pair of binoculars, the bigger the better.
Fortunately, I've been looking around long enough to know that there are many objects visible from the UK under average conditions, which I've listed below as the "Usual Suspects". Many are double stars, stars that look like one but when you see them with binoculars or a small telescope, actually turn out to be 2 or more. Some are a line of sight effect and are, in reality, much further away. Others are true binary systems which rotate around each other. Double stars are relatively easy to see, even under poor conditions.
Star clusters come in 2 flavours (although scientists are now saying the distinction isn't so clear): open and globular. Open clusters are a loose group, while globular clusters are more densely packed and, from a viewing angle, look much like galaxies with small instruments. The Pleiades are the most famous but thge nearby Hyades are an easier object under poor conditions.
Then there's the various types of nebulae, which have their light spread out over a large area, so become difficult in poor conditions. Fortunately, the Orion Great Nebula isn't too hard.
Once thought to be nebulae but were later (1920s) discovered to be "island universes" in their own right were the galaxies. Experienced deep sky observers won't agree but the only one easily visible from the UK and similar latitudes is the Andromeda Galaxy featured in many science fiction books and films.
Many deep sky objects have "M" numbers. These were assigned by Charles Messier (click here for details) to avoid anything that looked like a comet. His colleague, Pierre Mechain discovered a lot of the objects. They produced a "catalogue" of deep sky objects. Go to the bottom of the page for more catalogue links.
Alcor with Mizar
Alpha Persei Cluster (Melotte 20)
Hyades
Melotte111
Coathanger (Collinder 399)
Pleiades (M45)
Orion Great Nebula (M42)
Beehive (M44)
Nu Draconi
16 and 17 Draconi
Delta Lyrae
Epsilon Lyrae
Andromeda Galaxy (M31)
North America Nebula
