Title:NGC6888 ring nebula: a chemical enrichment lab.

Abstract:
Ring nebulae probe the chemical enrichment of the ISM by massive stars and, possibly, NGC6888 is the most studied Galactic 
ring nebulae. In this talk, we will review several properties of this object and present new optical spectroscopy obtained by 
HDS@8m Subaru telescope. For the first time, we have detected in this kind of objects the faint CII 4267 A recombination line. 
Combining these observations with photoionization models, we have been able to derive the total C abundance. Finally, we will 
also present archive narrow-band HST images with the aim of analyzing the ionization structure and the presence of 
shock-excited gas at small-spatial scales in selected zones.