The Soap Bubble Nebula

The Soap Bubble Nebula, formally designated PN G075.5+01.7, is a planetary nebula situated in the constellation Cygnus. It lies remarkably close (approximately 0.7° east) to the well-known Crescent Nebula (NGC 6888), which was the subject of my most recent published image.

This faint object was first identified by amateur astronomer Dave Jurasevich. His initial imaging, using a 160 mm refractor, was carried out in June 2007, and follow-up exposures in July 2008 confirmed the discovery.

As its popular name suggests, the Soap Bubble Nebula appears as a nearly perfectly spherical shell of ionised gas. Exceptionally faint and embedded within a diffuse Hα region, it escaped detection by all-sky surveys until the advent of deep CCD imaging. This combination of faintness and background nebulosity made the object particularly elusive.

The nebula spans approximately 4.3 arcminutes in diameter. Jurasevich’s discovery images revealed a shell measuring about 260 × 235 arcseconds. At an estimated distance of 4000 to 5000 light-years, its physical diameter extends across several light-years.

One of the nebula’s most remarkable features is its almost perfect roundness. Such spherical symmetry is rare among planetary nebulae (only about 20% exhibit this level of structural regularity) suggesting a uniform mass ejection from the progenitor star.

The central star is extremely faint, with a J-band magnitude of ~19.5, which is consistent with an evolved planetary nebula. Due to its relatively recent identification, the nebula does not appear in historical catalogues such as the NGC or Messier. In modern databases, it is typically listed as the "Soap Bubble Nebula" or PN Ju 1, in honour of Jurasevich’s discovery.

Image Acquisition

This dataset is the same used for my previous image of the Crescent Nebula (NGC 6888), as the Soap Bubble Nebula lies only 0.7° to the east and was captured within the same wide field.

During June and July 2025, I gathered exposure using Hα and O III filters, along with additional RGB data for the stars, in order to produce a final image in the HOO palette.

The data were acquired with my Takahashi TOA‑150 telescope and SBIG STL‑1000M camera, using Astrodon filters for Hα, R, G, and B, and a Baader filter for O III. The total integration time amounts to 34 hours.

Image Processing

As my main objective with this image was to highlight as much detail as possible of the Soap Bubble Nebula, the processing workflow (although based on the same dataset used for my NGC 6888 image) was significantly different.

Given the relatively small apparent diameter of the nebula, I opted for drizzle integration x2, resulting in a final image scale of 0.845″/pixel, compared to the "native" scale of 1.69″/pixel. This allowed for enhanced resolution and finer detail in the processed image.

Additionally, the parameters applied in the HDRMultiscaleTransform and LocalHistogramEqualisation tools were specifically adapted to suit the scale and morphology of the Soap Bubble Nebula, which is markedly different from the filamentary structure of the Crescent Nebula.

The first image on the right is a 100% resolution crop centred on the nebula, allowing close inspection of it. The second image presents a wider field view, showing the surrounding nebulosity in greater context.

Click on the images for full resolution versions, or go to the Gallery section for complete exposure details.

Image processing: Pixinsight.

Observatory automation and remote operation with  Talon6.