Horsehead Nebula - Orion

Object data: The famous Horsehead Nebula (dark nebula Barnard 33 (B33) in IC 434) in the constellation of Orion is one of the most photographed objects in the winter night sky. Just to the south of Alnitak, this region is dominated by the background emission nebula known as IC 434. High resolution images show this gas throwing off ionized partcles in response to the energised gases below. The projection of dark matter that forms the Horsehead is known as Barnard 33 (B 33), which is thought to be part of the same dust cloud that forms the dark lanes in the Flame Nebula. Date: 18/12/01; 19/12/01 Location: Southern France Conditions: 18/12/01: calm, transparency=8, seeing=7; 19/12/01: calm, transparency=9, seeing=7 Optics: RCOS Ritchey-Chretien 12.5" f/9 working at f/6.75 with AP focal reducer Mount: AP 900 GTO on Portable Pier Camera: SBIG ST-8E / CFW-8 Guiding: Integral ST-8E guiding chip controlled via MaximCCD Exposure: LRGB: Luminance: 14x10 minutes; RGB: 10:10:20 minutes binned 2x2 Processing: Image acquisition and calibration, combining, and (mild) DDP were done using Maxim DL, registration of Luminance and RGB images done using Registar, and a final linear stretch was done in Photoshop. Notes: I used the RC at f/6.75 with the intention of capturing a wider field, however the field I captured on the second night was not well aligned with the field from the first night and so after combining all the images the usable field was considerably reduced. Originally I estimated (visually) the seeing to be excellent on both nights, perhaps even under 2 arc seconds (I thought - it was so much better than is normal in southern France), however examining the stars in CCDOPS shows it to be about 3 arc seconds on both nights. Some hot pixels may remain in the above image - I was so intent on not inadvertently removing stars that I erred on the side of caution.