Walton, Oregon, September 24 and 30, 2022, August 11 and 13, 2023

The star WR 134 is one of a few Wolf-Rayet (WR) stars identified with an optical ring nebula.  The structure is a result of a strong stellar wind.  WR 134 is a variable Wolf-Rayet star located around 6,000 light years away from Earth in the constellation of Cygnus, surrounded by a faint bubble nebula blown by the intense radiation and fast wind from the star.  WR 134 is about five times the radius of the sun, but due to a temperature over 63,000 K it is 400,000 times as luminous as the Sun.  WR 134 was one of three stars in Cygnus observed in 1867 to have unusual spectra consisting of intense emission lines rather than the more normal continuum and absorption lines.  These were the first members of the class of stars that came to be called Wolf-Rayet stars named after Charles Wolf and Georges Rayet who discovered their unusual appearance.  It is a member of the nitrogen sequence of WR stars.  WR 134 has a spectrum with NIII and NIV emission between two and five times stronger than NV, leading to the assignment of a WN6 spectral type. The spectrum also shows a strong HeII emission and weaker lines of HeI and CIV. (Wikipedia)

WR 134 is classified as an Algol type eclipsing variable and given the designation V1769 Cygni, but the variation is not strictly periodic and brightness changes occur on timescales of hours to days. It has been investigated several times to search for companions.  Morel reported a 2.25 day primary period but considered the variations to be due to rotational modulation rather than the effects of a companion.  Rustamov suggests a 1.887 day orbital period with a K-M dwarf companion, but with additional optical variations.

Wolf-Rayet stars are extremely hot, bright, massive stars, and one of the rarest classes of stars known.  As of 2018, only 154 had been identified in the Milky Way, especially rare out of the one to two billion stars in our galactic neighborhood mapped and analyzed by the GAIA space telescope.  Some WR stars produce spectacular nebula, such as the Crescent nebula (NGC 6888), due to their strong stellar winds, intense ultraviolet emissions, and clouds of gasses that they shed in earlier stages of their relatively brief lives that end in a supernova explosion.  The nebula around WR 134 was first noticed in 1971.  Note that the blue structure is the result of shock waves of material expelled from the star that are colliding with and exciting a region rich in oxygen.  The nebula is embedded in the large nebula complex of Sh2-109, so the surrounding area is also filled with bright emission nebulosity. (NASA and others)

This image is a first attempt to highlight the faint Oxygen emission structure emanating from WR 134.  I intended this exercise to define the workflow for a complete dataset, but as I found a path to creating a decent image, I had invested many post-processing hours on my Mac.  It took quite a few iterations in PixInsight and Photoshop to achieve this result.  2X drizzle Hydrogen-alpha and Oxygen-III masters were created with the WBPP script.  I did not have flats for the OIII filter data, but dust donut artifacts were not apparent.  I used the Multichannel Synthesis script to blend 90% Ha to Red, 100% OII to Green and 110% OIII to Blue channels in the RGB combined image (HOO).  BlurXTerminator was used with mild settings as to prevent artifacts in the bright stars.  NoiseXTerminator was applied followed by SPCC to give the stars decent, but not entirely correct colors.  StarXTerminator was used to remove the stars which were stretched and saturated separately.  A starless luminance image was extracted, stretched with GHS, and processed for sharpness.  The starless RGB image was stretched using GHS iteratively and the colors were adjusted with a variety of tools.  The luminance was combined with the RGB color image.  The starless LRGB image was then processed in Photoshop to brighten the OIII structure with the Dodge, selective saturation and selective sharpening tools.  The LRGB image was combined with the stars in PixInsight.

I have posted this version while I decide if I need more data, narrowband for the nebula and RGB for the stars, or move on to the next target.  So many summer targets and so little time!

Imaging details:

Stellarvue SVX102T refractor with 0.74x focal reducer (FL = 528mm, f/5.2)
ZWO large off-axis guider with a ZWO ASI 174MM mini guide camera
Losmandy G11 mount with Gemini 2
ZWO ASI 2600MM Pro cooled monochrome camera (-5C)
Chroma 36mm Hydrogen-alpha, Oxygen-III, Red, Green, and Blue filters
Equatorial camera rotation: 0 degrees

Software:    Sequence Generator Pro, ASTAP plate solving, PHD2 guiding, 
    Losmandy Gemini ASCOM mount control and web client interface,
    SharpCap Pro for polar alignment with a Polemaster camera,
    PixInsight 1.8.9-2,
    Photoshop 2023

Hydrogen-a  10 min x 26 subframes (260 min), Gain 100, Offset 32, 1x1 binning
Oxygen-III    10 min x 45 subframes (450 min), Gain 100, Offset 32, 1x1 binning

Total integration time: 11.8 hours