M97 is one of the few planetary nebulae on Messier's list. It lies just under the 'blade' of he Plough, near the galaxy M108. At its centre is a white dwarf star, the remains of the star that shed the great cloud of dust we now see as the nebula. The two dark patches that give the nebula its name are caused by one of the 'shells' of gas having a hollow a barrel shape.
The photo below is only from three subs, taken whilst trying to track down M108. It will be updated when a better image is available, but for now you can just make out the blue-green colour, the two dark patches and the hint of three stars including the central white dwarf.
M97, the Owl Nebula
Here is Lord Rosse's famous drawing of the Owl Nebula, imaginative but not bad for a visual observation, although he moved the central star into an eye socket. One of his clerical friends suggested it looked like 'the visage of a monkey'. Quite an engaging little chap if you ask me.