Sh2-308, also designated as Sharpless 308, RCW 11, or LBN 1052, is an H II region located near the centre of the constellation Canis Major, composed of ionised hydrogen. It is about 8 degrees south of Sirius, the brightest star in the night sky. The nebula is bubble-like (hence its common name, the Cosmic Bubble – though more commonly known now as the Dolphin Nebula), surrounding a Wolf–Rayet star named EZ Canis Majoris. This star is in the brief, pre-supernova phase of its stellar evolution. The nebula is about 4,530 light-years away from Earth, but some sources indicate that both the star and the nebula are up to 5,870 light years away. Yet others indicate the nebula is as close as 1,875 light years from Earth.[6] Sh2-308 surrounds the Wolf–Rayet star EZ Canis Majoris, also designated EZ CMa or WR 6. Its apparent magnitude varies from 6.71 to 6.95. Its spectral type indicates that the star is very hot and luminous. The spectrum shows that it is devoid of hydrogen at the surface. EZ Canis Majoris is expected eventually to explode in a supernova, therefore subsuming the nebula.
Imaging telescope: Takahashi FSQ130ED
Imaging cameras: QSI 6120i
Mounts: Takahashi EM 400 Temma 2
Guiding cameras: QHY CCD QHY 5 II
Focal Extender / Reducer: Tak QE 0.73x
Software: PHD 2, Astro Pixel Processer, PixInsight , Sequence Generator Pro SGP
Filters: Astrodon Ha (5nm) & OIII (5nm)
Dates: Jan. 31 – Feb. 13, 2021
Frames:
Astrodon Ha: 21×900″
Astrodon OIII: 22×900″
Integration: 10 Hours 45 Mins.

Autore: Brendan Kinch (sito)