ShinyPhoto

Around 725pc (2400ly) distant, the Cygnus Loop (aka Sharpless Sh2-103) is an emission nebula in Cygnus measuring nearly 3° across, a large supernova remnant caused by a star around 12-15 solar masses (as yet unidentified).

I've had it in mind to make a photo of this entire loop for some months. This was comparatively tricky - with the appalling weather this summer, I decided OSC was the way to shoot it and preferably all in one frame without relying on a mosaic. Accordingly, I rigged-up a new astro-camera (the RisingCam IMX571 OSC) to my old Sigma 100-400mm (EF-mount) lens.
I also upgraded my dual-narrowband filter from the Optolong L-eNhance (which passes H-beta, making it not pure dual-NB) to the IDAS NBZ (which is pure Ha & OIII only, with no flare on bright stars).

It's been fun watching this come together. Initial attempts using 180s subs proved too dark, so I abandoned them and spent a couple of hours each of several nights shooting 300s subs instead.

Finally, in processing, experiments with background neutralization revealed far more nebula tendrils than I'd expected. I'd been looking for a coat-hook/screw shape with the bulk of the Eastern and Western Veil nebulae including the Witch's Broom nebula on the right, along with a "tail" toward the botom, but was not prepared to find an extra halo of Ha in an arc around the top of the structure.

Data:
62 * 300s lights, IDAS NBZ filter, 100-400mm lens at ~258mm
64 flat frames
266 dark frames
128 bias frames