This image is a collaboration between Michael Rushalko and Bob Fugate. Michael suggested the target supernova remnant G65.3+5.7 as something new and a bit different. A search on AstroBin returns only 87 images. It does not seem to have a common name.

The supernova remnant G65.3+5.7 was discovered by T. R. Gull, R. P. Kirshner, and R. A. Parker in 1977 during an OIII survey of the Milky Way. Some parts of this remnant were previously cataloged by Stewart Sharpless in his SH2 catalog as SH2-91, SH2-94, and SH2-96, but they were not recognized as part of a larger supernova remnant at that time. The idea that these could be part of a bigger structure was postulated by Sidney van den Bergh in 1960, but it was not confirmed until 1977. Thus, 1977 marks the year it was first cataloged as a supernova remnant.

It is a very large, evolved SNR notable for being identified as a SNR through optical observation using deep Hα and OIII imaging revealing filamentary structure. Unlike many SNRs initially detected through radio or X-ray emissions, G65.3+5.7’s discovery is significant for its optical identification, a rarer method due to the remnant’s faintness and location in a low-density region of the galaxy. It is listed among Galactic SNRs in catalogs like Green’s (2022), indicating its confirmation as an SNR based on its morphology and spectral characteristics.

G65.3+5.7 is located in the Galactic plane at coordinates l = 65.3°, b = +5.7° (Galactic longitude and latitude). This places it in the constellation Cygnus, a region rich with other SNRs like the Cygnus Loop. Its position is approximately 5.7 degrees above the Galactic plane, which is relatively high, contributing to its faintness in radio and X-ray due to the low-density interstellar medium (ISM) in that region.

G65.3+5.7 is one of the largest known SNRs, with an angular size of approximately 310 arcminutes × 240 arcminutes (roughly 5.2° × 4°), making it comparable to other large SNRs like the Vela SNR and the Cygnus Loop. At an estimated distance of 0.8–1.0 kpc (2,600–3,260 light-years), its physical diameter is approximately 70–90 parsecs, indicating an evolved remnant in the radiative phase of its evolution. The remnant exhibits a shell-type structure with thin, arc-shaped optical filaments, particularly along its eastern limb. The remnant is estimated to be 90,000–110,000 years old. Its location 250–300 parsecs above the Galactic plane explains the lack of strong radio or X-ray signatures, as the sparse ISM limits shock interactions.

G65.3+5.7 is significant for being one of the few SNRs discovered optically, highlighting the potential for finding additional high-latitude SNRs that escape radio and X-ray detection due to their environment. This challenges the completeness of SNR catalogs, which estimate ~2,000 undiscovered SNRs in the Milky Way.

We observed G65.3+5.7 at Starfront Observatories over 5 nights from May 11 through May 29, 2025. We have nearly identical rigs based on RedCat 51 telescopes, ZWO ASI6200MM full frame cameras, 3 nm narrowband filters, Pegasus V2 Falcon rotators, and ZWO AM5 mounts. We are located on neighboring piers in Building 3 at Starfront. The image here represents a total of 34 hours and 24 min of integration including 22 hours and 50 min of OIII data. Even though we collected 50 min of SII data we did not include it in the image.

We used PixInsight and Photoshop for image processing. PI was used to prepare TIFF files as input to layers in Photoshop. All files were cropped to eliminate rough edges from stacking. WBPP in PI created masterlights for Ha, OIII, SII, R, G, and B using CosmeticCorection and LocalNormalization. The R, G, and B files were combined, gradient corrected, plate solved, de-convolved with BlurX, color balanced with SPCC, stars extracted with StarXTerminator, stretched with HistogramTransformation, and saved as a 16 bit TIFF. The starless RGB file was auto-stretched and saved as a TIFF - it was used as a foundation layer in Photoshop to provide more contrast to the dark regions. The narrowband images were gradient corrected, sharpened, stars extracted, auto STF applied, stretched in HistogramTransformation and saved as 16 bit TIFFs.

In Photoshop the RGB stars, Hα, OIII, SII, and RGB starless (top to bottom layers) were loaded as layers and then converted to groups allowing editing of individual layers. All layers were set to Screen blending mode. The narrowband layers were colorized with a Hue/Saturation adjustments layer, the brightness was adjusted with Levels adjustment layer, in some cases (OIII primarily) curves and luminosity masks were used to increase contrast of faint structures and filaments in the SNR. We find it easier to use Photoshop to make subtle level and contrast adjustments in real time non destructively than using PixInsight for the same functions. After adjusting individual layers, the image was flattened and saved as a TIFF file and as a JPEG file for uploading to AstroBin.

Please drive around at full resolution. The filaments in this SNR are among the most gorgeous in the sky anywhere:

OTHER OBJECTS IN THIS IMAGE

There are four entries from the Sharpless catalog of H II regions, three of which are part of G65.3+5.7. Sh2-91, -94, and -96 are components of the SNR and Sh2-92 is the large H II region to the left of the SNR in this image:

Other objects of interest include:
NGC 6813

which SIMBAD lists as an Interstellar Medium Object;

and in the top left corner NGC 6842

which SIMBAD lists as a Planetary Nebula;

and in the lower right, either a galaxy PGC 63084 (PixInsight) or a supernova (SIMBAD):

Also in the lower left these structures which we have not been able to identify.
Can anyone help identify this bright red object?