SH2-129 (Flying Bat Nebula) and Ou4 (Squid Nebula)

SH2-129 and Ou4
All Images Copyright Steve Cannistra

Please click here or on image above for a medium-sized view (40%)

Magnitude:  Not determined
Size: FOV of full frame image (4096 x 4096 pixels) = 3.9 x 3.9 degrees
Image scale:  3.5 arcsec/pixel
RA: 21h 09m 40s (J2000)
Dec: 59 degrees 58' 20" (J2000)
PA:  +353 degrees

SH2-129 is a relatively faint emission nebula in Cepheus, a neighbor of the larger and more often imaged IC 1396.  Sometimes referred to as the "Flying Bat" nebula, this region is characterized by Ha emission as well as a small, mixed emission and reflection nebula (vdB 140), seen in the lower portion of the field, just to the left of center.  What is most remarkable about this region is a recent discovery made in 2011 by Nicolas Outters, called the "Squid Nebula" due to its shape, but more officially called Ou4.  This region is characterized by a very faint OIII emission that has a bipolar shape reminscent of a planetary nebula, seen as the teal-colored region just to the left of center and requiring 10 hours of imaging through an OIII filter to capture (and could have used even more!).  Although it was originally thought to perhaps represent a planetary nebula derived from an unknown, dying star, more recent evidence suggests that Ou4 is located within SH2-129 itself and is a bipolar outflow emitting in the OIII spectrum, moving at the same rate as SH2-129, and possibly emanating from a triple star system located in the center of Ou4 (HR8119, visible above as the bright star in the center of the Squid).  More information about this region may be found here.

Photographic Details:
Dates:  August 25, 26, 27, 28, 2015
Scope:  Takahashi FSQ106 at f5 on the Takahashi NJP Mount
Autoguider:  SBIG ST-402 with 60mm guidescope, focal length 227mm
Camera:  Apogee U16M at -20C, with 7 position 50mm square filter wheel (Apogee FW50-7S)
Baader narrowband and LRGB filters, 50mm square
Exposures:  Ha, 4 hours; OIII, 10 hours; RGB, total of 6 hours.  Total combined exposure (Ha, OIII, RGB) = 20 hours
Post-processing:  Calibrated, aligned, and stacked in Maxim, followed by DDP in ImagesPlus (IP).  Further processing in Photoshop CS (16 bit format).  The luminance signal in the above image represents a composite of Ha and OIII.  The RGB color is provided by R-Ha, G-OIII, and B-OIII channels, respectively.  The OIII signal from Ou4 was very weak and required several hours of processing that included sequential curves adjustments, selective use of screen mode with appropriate masking, as well as mild use of noise reduction with Noise Ninja.
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