Horsehead Nebula Nebula Enlarge Description The H-a image: Image Date: 11/23/2004Details: Exposure Time: 4 hrs Total; 2.5 hrs H-a, 30 min each RGBCamera: SBIG ST-10XMETelescope: RC Optical Carbon 12.5 inch f/9 Ritchey-ChretienMount: Software Bisque Paramount ME