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In August 2025, several of us at SFRO were each individually capturing the Helix Nebula. Through conversation on the SFRO discord, someone had the idea to combine all our images together to amass a ridiculous amount of integration time - @Naveen Ravindar created a group thread and thus this collaboration group was born! Over the next several months, everyone in the group captured images with their own telescope gear using the same framing. 14 types of telescopes were used in this collaboration with focal length ranging from 250mm from an ultrawide WO Cat 51 to 1645mm from a 9.25” EdgeHD. Many thanks to everyone on the team for all their hard work and time put into this project!

Processing Details:

For image preprocessing, everyone calibrated their own images, culled bad subframes, and stacked all their frames for each filter. Both PixInsight and AstroPixelProcessor were used in stacking master frames for each team member. All the master frames were then uploaded to a shared Google Drive for everyone to try their hand at combining. After some trial and error, @maxsid successfully combined all the contributor master frames in APP using @Stephan Trzeciak image as the reference frame. The 840mm focal length of Stephan’s system was an ideal resolution of 0.92” per pixel.

The image revision seen here was processed by @Jonathan Hill using PixInsight and Photoshop. The RGB data was processed to emphasize the stars, background galaxies, and some inner disk broadband color and the narrowband data was layered on top using a custom SHO palette inspired by the Hubble Space Telescope’s Helix image.

Noise reduction for this image was a little more complicated than usual. Due to interpolation in the image registration process matching wide angle images with the tighter FOV of the reference image, the noise profile was rather coarse. This caused neural network tools such as NoiseXterminator to hallucinate stars and background galaxies in the noisiest parts of the image and for fine details in the fainter nebulosity to be lost. To solve this, a light pass of MultiscaleMedianTransform was used to reduce noise on primarily the medium sized wavelet layers. This provided a much better baseline for NXT to work with. Using a combination of these two tools provided much better preservation of fine details and faint nebulosity than either provided alone. TGVDenoise, MultiscaleLinearTransform, and GraXpert denoise were all tested as well, but showed less pleasing results than MMT + NXT.

Scientific Information: written by @Naveen Ravindar

The Helix Nebula (NGC 7293, Caldwell 63) is one of the closest planetary nebulae to our solar system sitting only 655 ly away in the constellation of Aquarius. Its closeness allows a deep look into its internal and extended structures with a fidelity not easily achievable for most other planetary nebulae. By combining datasets from wide-field refractors with larger reflectors and catadioptric systems, the faint extensions of the nebula are revealed while maintaining a high degree of detail on the cometary globules at the nebula’s heart. Our deep integration of narrow and broadband images of this nebula showcases an incredibly complex polypolar structure with ejecta in a multitude of directions out to 5 ly or more from the central star. The faint extended halo far exceeds the commonly stated diameters for this nebula.

Figure 1: An annotated image of the Helix Nebula showing the inner and extended structures of the nebula as interpreted by the SFRO Helix Collaboration Team.

Figure 1 shows an annotated image of the Helix Nebula and its extended halo based on apparent morphology and undisputed spectroscopic measurements alone. Starting from the middle of the nebula an innermost ring, bright in the IR can be seen against the larger central Oiii (blue) emission. Farther out, the bright yellow and and orange features that give the helix nebula its name are present, decorating their boundary with the inner disk.

Continuing away from the central star, NW and corresponding SW plumes can be seen among radial Oiii striations. These Oiii radial rays are believed to be emission not in plane with the helix structure itself but to be “above and below” a ring of material in the helix region of the nebula. These striations terminate at the NE and corresponding SW outer arcs, with the NE arc sometimes being referred to by imagers as the eyebrow that sits above the eye. In the gaps between these brighter outer, arcs jut through NW and corresponding SE ejecta features.

Now for the fun faint stuff! Never before seen in such detail, six or more H-alpha emitting bow shocks can be seen toward the NE of the nebula, where ejecta from the nebula interact with the surrounding ISM (interstellar medium). Variations in density in the ISM and ejecta velocity lead to a multitude of smaller bow shocks within the larger shock fronts. These bow shocks are formed by the combined velocity of the ejecta relative to the central star, and the bulk motion of the object and central star summing up to a high enough speed relative to the ISM for shocks to form. The trailing SW ejecta is believed to have a similar velocity relative to the central star as the NE ejecta but is moving against the bulk motion of the nebula, leading to speeds relative to the ISM being insufficient for the formation of such bow shocks.

This disparity in ejecta behavior can also be seen among the NE and SW outer arcs, with the NE arc showing a clearly defined edge likely due to a compression of material as it ploughs through the ISM, while the SW arc shows a more loosely defined, dispersed, and tenuous structure.

Among the SW ejecta a jet of material can be seen, the speed of which has been estimated by J. Meaburn et al to be ~300 km/s, dwarfing the ejecta speeds of the inner regions of the nebula at some 20-40 km/s. Often referred to as the Meaburn Jet, its high recessional velocity relative to us and the central star cannot be easily discerned by analyzing its morphology alone. Even farther out from the shock fronts, an extremely faint extended halo can be seen extending 5 ly and more in radius from the central star.

The 3D Structure of the Nebula:

In researching our current understanding of the structure of the nebula, two noteworthy interpretations of its structure have been put forward, one by John Meaburn and collaborators, and one by C. R. O’Dell and collaborators. Both groups agree that the nebula likely exhibits a polypolar structure with ejecta along multiple axes, but significant disagreements exist between the two over the salient details.

C. R. O’Dell and collaborators suggest an inner disk of material tilted 23° from our line of sight with the plumes and features lined up with a PA of 125° (PA: Polar angle) being along the same axis of the inner disk. The bulk of the extended structure is interpreted by them as a a disk of ejecta nearly perpendicular to the inner disk, tilted at 53° from our line of sight, with the inner most region of this ejecta composing the bright helical structure that gives the nebula its name.

Figure 2: The C. R. O’Dell et al Interpretation of the Helix Nebula on the SFRO Helix collaboration team image. The faintest extended features are not mentioned by O’Dell et al.

John Meaburn and collaborators have suggested that rather than a disk of ejecta creating the extended halo and helical structure, 2 bipolar structures instead comprise the features we see. In the annotated image, a CO torus is also labeled although it cannot be seen in this LRGB-SHO image.

Figure 3: The Meaburn et al Interpretation of the Helix Nebula on the SFRO Helix collaboration team image.

As far as the extended regions of the nebula are concerned, the bipolar structure proposed is more compelling, in my opinion, rather than the alternative disk-like structure. This assessment is based on the spectroscopic data of Meaburn et al. The high velocity Meaburn jet with velocities estimated at 300 km/s and being collisionally ionized with their reported Ha/Nii brightness ratio, suggests it is a collimated flow. This provides more evidence for a strongly axially aligned feature rather than a disk for the faint extended emission. The high recessional velocity of the jet also does not fit the morphology suggested by O’Dell and collaborators. O’Dell et al. have also not yet commented on these faint external features or provided spectroscopic evidence for their interpretation, relying on the morphological data alone.

Without commenting on the inner structure of the nebula, our deep image of the Helix nebula, taken along with past velocity estimates, suggests a dual bipolar structure for the observed extended emission. The suggested structure consists of an inner bipolar flow along a PA of 125° and an outer bipolar outflow along a PA ~70-75°. Assuming the ejecta velocity vector of the NE bow shocks relative to the central star lies along this NNE polar angle, when accounting for the bulk velocity of the nebula relative to the ISM, the bow shock direction at a PA of 84-86° is expected, which appears to be supported by the multiple bow shocks evident in our image.

Figure 4: A poly-polar interpretation of the extended features of the Helix Nebula. This image uses blue arcs for features in the nebula with processional velocities and red for recessional velocities after compensating for the motion of the central star.

What at first appears as a close common representation of a planetary nebula when imaged deeply reveals a complex polypolar structure with a multitude of large ejecta events, evolving over many thousands of years, with our image revealing features whose material was ejected before any helical structures were formed. In researching this write up I have now truly understood how challenging it is to reveal the 3D structure of the objects we see in our night sky regardless of how close and well known they are.

As of February 2026, there does not exist sufficiently deep IFU or spectroscopic data of the central and extended regions of the Helix nebula to confidently reveal the full intricacies of its 3D structure. However, I hope that the extended faint emission our image reveals inspires professional astronomers to collect more data and determine the motions and multipolar structure of this nebula. For now the Eye of God still keeps some secrets.

Image Revisions:

Several other team members processed the data into excellent revisions. The final revision was chosen via group input and voting.

Processed by @Jeremy Phillips FRAS
JezAstro Helix.jpg Processed by @jmdl101
jmdl101 final processed compressed.jpg Processed by @maxsid
maxthebuilder_from_collab_masters_JanCux_as_reference.jpg Processed by @NE-FL-Astro
NE FL Astro Final Image2.jpg

Additional Information:

Here is a comparison between the stacked, unprocessed master frames with an extreme STF applied:

raw frame comparison.jpg
Here are some summary tables showing the team members who contributed to this collaborative image and their individual contributions. Once again, many thanks to everyone on the team for all their hard work and time put into this project!

Contribution tables.jpg *An additional 3 hours of acquisition is shown in these tables from L data captured by JanCux. It was not used to produce the final image, so it is excluded from the acquisition details.