planetary nebulae

sites with cool pictures:

http://commons.wikimedia.org/wiki/Image:Planetary_nebulae_He_2-47_NGC_5315_IC_4593_NGC_5307.jpg

http://www.wadih-ghsoubi.com/Astronomy/4/index.html

http://www.nightskyinfo.com/planetary_nebulae/

http://www.uv.es/jrtorres/index6.html

http://www.skyandtelescope.com/observing/objects/deepsky/3305491.html?showAll=y&c=y