NGC 6751 - ATT 2,3m - Hua, Dopita, Martinis (RGB; [NII], Ha, [OIII])
NGC 6751 - NTT/ESO - Schwarz, Corradi, Melnick (RGB; Ha+[NII], both, [OIII])
NGC 6751 - Hubble Space Telescope - Hajian et al (unpublished)
NGC 6751 - Hubble Space Telescope - NASA and The Hubble Heritage Team (STScl/AURA)