SFO 82-The Dark Tower Nebula (part from RCW 113 also Gum 55), and reflection nebulae vdBH73a-e near NGC 6231 in Scorpius

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    12" ASA: LRGB 12" ASA: LRGB - crop    
    Size: 2000 px Size: 2000 px    
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© Velimir Popov & Emil Ivanov 2013

RCW 113, also called Gum 55, is a huge region of diffuse nebulosity surrounding the Sco OB1 association and its core ionising cluster NGC 6231. This region is a large roughly semicircular loop, and at its centre is the cluster NGC 6231. In this scene NGC 6231 is outside in direction SE (upper-right on the image). The Dark Tower - SFO 82 (SFO - designation of Bright-rimmed Molecular Clouds), the prominent bright-rimmed cometary globule, lies about 1.5 degrees away (NW) from the NGC 6231 and Zeta Scorpii.

The shape of this massive structure of cosmic dust resembles a dark tower emerging from the star field background. Within the top of the tower the image shows several bluish reflection nebulae (vdBH73a-e) exited by intense radiation of hot O-type stars. These structures are stellar nurseries. Typical of the Cometary Globule are the stellar winds coming from the head towards the tail. The energetic ultraviolet light also causing the red glow (from hydrogen gas) of the extensive bright rims (emission nebulae) around the top of the Dark Tower and the background medium. SFO 82 and associated nebulae are about 5 500 (+/- 1000) light-years away.

This is an image taken with 12" ASA astrograph. An image taken with 16" Dream Corrected Astrograph (DCA) can be seen here

Object details

Right Ascension 16 46 50 (h:m:s)
Declination -41 13 54 (deg:m:s)
Distance ~ 5 500 (ly)
Apparent Dimension - (arc min)

Image details


Center of field RA 16:45:42 (h:m:s)
Center of field DE -41:07:23 (deg:m:s)
Size 56.9 x 42.6 (arcmin)
Pixel scale: 1.03 (arcsec/pixel)
Orientation: Up is -1.62 degrees E of N


Charts and image details obtained from Astrometry.net
Optic(s): ASA 12" f 3,6 Astrograph (ASA)
Mount: ASA DDM85
Camera: FLI MicroLine 8300 CCD camera
Filters: Lum, Red, Green, Blue, Ha, OIII and SII Astrodon
Dates/Times: From 3 to17 of May 2013
Location: Namibia-TIVOLI ASTROFARM, S 23° 27' 40,9" / E 18° 01' 02,2"
Exp. Details: L: 7x10min, R: 5x10min, G: 5x10min, B: 5x10min, Bin 1
  Total Exposure Time - 220 min (3:40 hours)
More details: Dark and flat frames reduction
Processing: PixInsight / PS
Copyright: Velimir Popov and Emil Ivanov 2013. All Rights Reserved
e-mail: info@irida-observatory.org
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