A supernova remnant in Cassiopeia. It was first classified as planetary nebula. But recent measurement suggest it to be the shockwave of a supernova blast about 10000 years ago at a distance of 10000 light years. The bubble has now a diameter of approximately 100 light years.
This object is pretty faint and difficult. The image has been acquired over three nights, partly through high clouds.

Here a few crops.

The following image shows the difficulty with this object. This image is the result of only about 3 hours integration. The number of stars in this field is enormous. Longer exposer time also increases the number of visible stars and in becomes more and more difficult to separate stars and nebula parts. Whatever method is used to deemphasize the stars, artifacts become visible unless a lot of manual work is executed to remove these artifacts. In the pictures above dark halos are visible around brighter stars which is due to imperfection of the star removal process used in the workflow.

Acquisition Details

Scope: Borg 90FL/500 with 1.08x Flattener
Filter: IDAS NBZ
Camera: ZWO ASI 2600MC Pro
Mount: Skywatcher HEQ5 Pro
Guiding Scope: MiniBorg 50
Guiding Camera: ZWO ASI 290MM
Guiding Software: PHD2
Acquisition Software: APT
Light Frames: 90x300sec in three nights
Flats, Dark Flats, Bias, Darks
Camera settings: Gain 100, Offset 20
Bortle 4-5, no moon
Acquisition Dates: August 09,10,11 2021

Processing

Imaging & Stacking: PixInsight
Denoise: Topaz AI Denoise
Star halo removal: Gimp