Planetary nebulae, the remains of dying stars, glow primarily by the light of energized oxygen, which is in the green part of the spectrum. That gives this bright, concentrated nebula its striking blue-aqua glow. It is rare for the human eye to see color of celestial objects other than planets in the telescope; this one is a real treat. 15" F/5 Dobsonian, 8mm LVW eyepiece (240x). Lake Sonoma Recreation Area, CA. 2008-08-30.