Lorenzo Comolli's Astronomy HomePage

Click on the image for high res version. MOUSE OVER for starless. Look below for a GIF animation of all image versions.
Hires links: Stars+Nebulae , Nebulae only , Stars only , H-alpha starless , H-alpha with stars , OIII starless , OIII with stars.

This is an emission nebula in Cassiopeia. The main emission light is in H-alpha red wavelength, but there is an interesting central part with OIII emission superimposed on the H-alpha emission. This superbubble was created by a central star, that emitted the gas and expended due to the stellar wind. It is 7500 light years far and 44 light years diameter, corresponding to 20'.
The processing was aimed to evidence the faint background due to the Cassiopeia stellar association and the color of the OIII central emission. A fundamental step of processing was the removal of stars by means of StarNet++ algorithm by Nikita Misiura. Look to all the above versions with and without stars.
Imaging was taken during the 2024 Saint Barthelemy Star Party.

GIF animation of all image versions in this order: Stars+Nebulae , Nebulae only , Stars only , H-alpha starless , H-alpha with stars , OIII starless , OIII with stars.

Here below some other shots of the setup and the star party

Technical Data
Optics	TEC 140
Focal Length	1011 mm
Focal Ratio	f/7.2
Exposure Time	Total 9 h 10 min, composed of Ha-OIII-RGB 400:70:20:20:20 min (single exp of 10 min for Ha and OIII, and 5 min for RGB)
CCD	ZWO ASI 6200 MM @-20°C
Location	Saint Barthelemy, Leyssè area (AO, Italian Alps) at 1600 m height
Date	27-28 September 2024 (2 nights)
Mount	Gemini G-41
Tracking	ZWO ASI 174 mini on an 80mm f/5 refractor
Temperature and humidity	T= (+3 to -1) °C, RH=(55 to 75) %
Sky brightness at zenith (with SQM-L)	(21.1 to 21.4) mag/arcsec^2
Notes	Quite clear and dark nights, except the first part of the first night.