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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 (visible as a vertical 'spray' in the above image). The projection of dark matter that forms the Horsehead Nebula is known as Barnard 33 (B 33), which is thought to be part of the same underlying dust cloud that forms the dark lanes in the Flame Nebula. This is a high resolution image, complementing my earlier wide field image of this region, which also includes Alnitak and the Flame Nebula.
Date: 12/11/09; 18/11/09
Location: Southern France
Conditions: 12/11/09: calm, transparency=9, seeing=8; 18/11/09: calm, transparency=7, seeing=7
Optics: RCOS 12.5" Ritchey-Chretien with custom field flattener working at f/9.5
Mount: AP 900 GTO on Portable Pier
Camera: SBIG STL-11K, SBIG LRGBC filter set, -30°C
Guiding: Integral STL-11K autoguider
Exposure: LRGB Seq: 19x 20 minutes; 5x 20 : 13 : 20 minutes (binned 2x2).
Processing: Image acquisition, calibration, combining, and DDP were done using Maxim DL, registration of Luminance and RGB images done using Registar, and final processing was done in Photoshop CS4.
Notes: This was essentially a first light test image after having the RCOS Secondary recoated. As others may know this is quite an 'invasive' procedure (at least in the case of the RCOS) and involves far more than a primary recoat. At the same time I decided to clean the primary and following all of this the next big task was to recollimate the whole optical train. Overall I think it went quite well and after repeated testing I think that collimation is close to optimum, as I hope the above image helps demonstrate. There is a slight anomaly with the upper-right spike from the bright mag. 7.7 star to the north of the Horsehead (left in this photo) but I think this was due to a misaligned secondary control cable which is attached to that spider vane.
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