Caldwell 15 (NGC 6826) Blinking Nebula

This small planetary nebula has an unusualy bright central star which is surrounded by a faint nebula. Why is it known as the blinking nebula? When observing this planetary through a telescope, when you look at the star, the nebula dissappears. When you look slightly away, the nebula suddenly reappears. This occurs because the eye is more sensitive slightly to one side of the center of vision. The two bright patches to the lower left and upper right of the nebula have caused much debate and are still not well understood.