Interstellar shells in Cassiopeia

I am very happy to present the second image in which these interstellar shells can be seen at all, and at the same time, it is the first photo to show the shells so clearly thanks to the long exposure time.

Thanks to several clear nights in the fall, I was able to collect nearly 39.5 hours of narrowband data with the RASA at f/2, along with an additional hour of RGB for the stars. The processing was certainly challenging, but I managed to bring out many details in the OIII structures and the surrounding H-alpha clouds.

 

A few details about the objects in the image:

The bluish filaments in the center are listed in Simbad as “interstellar shells” with the designation GSH 122+02-77. These are not direct supernova remnants but rather part of the interstellar medium (ISM)—low-density material (mostly gas) that exists between stars. Stellar winds and nearby supernovae can interact with this material, forming irregular shells. The neighboring Wolf-Rayet star HD 4004 (WR1) could possibly be responsible, although there are no definitive research results on this yet.

In the upper left, you can see Sh2-181 with a pronounced OIII shell, while Sh2-175, a small emission nebula, is located on the right.

 

Celestron RASA 8 400mm f/2

Celestron Motorfocus

EQ6-R Pro

Camera 1 (OSC): ZWO ASI 2600 MC Pro (Gain 100, Offset 18, -10°)

RGB (Stars): 65 × 60″ (1h 5′)

Camera 2 (Mono): TS 2600 MP (Gain 100, Offset 200, -10°)

Baader H-alpha Highspeed Ultra-Narrowband 3.5nm Filter): 700 × 120″ (23h 20‘)

Baader OIII Highspeed Ultra-Narrowband 4nm Filter): 483 × 120″ (16h 6‘)

Total: 40h 31‘

Bortle 5 (19.50 SQM)

N.I.N.A., Guiding: ASI 120MM & PHD2

Astropixelprocessor, Photoshop, Pixinsight

Done