SNR G115.5+9.1 – Scylla – Deep Sky Collective
Scylla is a recently discovered supernova remnant candidate in the constellation Cepheus, sitting at an unusually high galactic latitude, which makes it a rare find. It was first published in April 2025 by Marcel Drechsler et al. and at the time we began imaging it, only three other hobbyists had photographed it on Astrobin. Because the discovery is so recent, fundamental properties including age, distance, and expansion speed remain unknown. What drew the Deep Sky Collective to it was the combination of its interesting morphology, its location in an IFN-dense field, and the fact that the existing images hadn’t gone deep enough to fully reveal its structure.
The project
We began imaging Scylla in August 2025 and collected data over roughly four months, with pre- and post-processing following in February. 13 contributors were involved across coordination, stacking, editing, and photography. Total integration came to 538 hours and 15 minutes, with around 200 hours each in Ha and OIII and the remainder primarily in LRGB. A small amount of SII data (around 5 hours) was collected to check for signal, and while something did show up, there wasn’t enough to incorporate into the final edit. In retrospect the Ha and OIII turned out brighter than expected, which means SII would have been worth pursuing more seriously.
What the data revealed
The Ha data showed the full shell along with a number of previously unseen fine-scale details. It also revealed what appears to be foreground Ha in the form of curtains running across the image, which required careful handling during processing, particularly in the continuum subtraction, to separate from the SNR itself. The result is what we believe to be the most accurate representation of Scylla’s morphology produced to date.
The OIII data added further extensions of the SNR not previously documented, along with additional detail. A bright star sitting within the main OIII bow presented a processing challenge that took some work to manage without compromising the surrounding structure.
A potential new discovery
The dataset also contained something unexpected: an object we believe may be a previously undocumented planetary nebula or similar structure. It forms a double-sided bow shape, comparable in form to the Goblet of Fire nebula but smaller, and we believe its isolated geometry argues against it being part of Scylla. There is a white dwarf in the vicinity, though it sits just outside the shell rather than at the centre. Central coordinates are 23h 28m 18.5s +70° 57′ 23.2″ (SIMBAD). Further updates will be added to this page as they become available.
Two versions
The dataset was processed independently by two editors. Steeve Body’s edit is the main published version, with Nicolas Puig’s edit also available.
Integration
Ha: ~200h / OIII: ~200h / LRGB: remainder / SII: 5h / Total: 538h 15m
Credits
Tim Schaeffer (coordination), Carl Björk (stacking and photography), Steeve Body (editor), Nicolas Puig (editor). Photographers: Jasper Capel, John Dziuba, Justin P., Stephen Guberski, Akash Jain, Jim Matzger, Logan Carpenter, Alpha Zhang, Jeff Schilling.
Full image at https://deepskycollective.com/gallery.