NGC 6995, The Bat Nebula

NGC 6995
All Images Copyright Steve Cannistra

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RA (J2000): 20h 56m 14s
Dec (J2000): +31 degrees 26' 07"
Position Angle: 90 degrees

The Bat Nebula (NGC 6995) is located in the eastern portion of the Veil Nebula Complex.  This entire region is created by an expanding shockwave resulting from a supernova that exploded approximately 8,000 years ago.  The shockwave slams into surrounding dust in the interstellar medium, ionizing gases such as hydrogen, oxygen, and sulfur, which emit specific wavelengths of radiation during electron recapture.  The above image was taken though two filter, one that passes radiation from singly ionized hydrogen (HII, Hydrogen Alpha, 656.3 nm, shown in red) and another that passes radiation from doubly ionized oxygen (OIII, 496nm and 501nm, shown in blue).  The result is a beautiful, lacelike structure that has fascinated astronomers since its original discovery in 1784 by William Herschel. The filamentous structure of the nebula results from the fact that we are viewing the thin shockwave fronts edge-on.

Photographic Details:
Dates:  August 23, 2023.
Scope:  Takahashi FSQ106 at f5 on the Takahashi NJP Mount.
Autoguider:  ASI178 autoguider with SvBony 30mm guidescope, focal length 120mm.
Camera:  ZWO ASI294MM at -10C, with 7 position ZWO filter wheel.  Pixel size is 2.3 microns (Bin 1x1), yielding an image scale with the FSQ (530mm focal length) of 0.90 "/pixel (well matched for my seeing of  3 arcseconds).  Camera gain set to 50 (e-gain 2.13 electrons/ADU), offset 25. Read noise at this gain level was 2.18 electrons rms.
Baader Ha, OIII filters; 2 inch.
Image acquisition software:  MaximDL for camera control and autoguiding; CCD Commander for automation.
Exposures:  Total exposure 4 hours (Ha: 2 hours, 300 second subs; OIII 2 hours, 300 second subs).
Processing:  Calibration, integration, deconvolution (BlurXTerminator), noise reduction (NoiseXTerminator) in Pixinsight; subsequent processing in Photoshop.

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