The Rho Ophiuchi Nebula – Antares

is a multiple star system in the constellation Ophiuchus. The central system has an apparent magnitude of 4.63. Based on the central system’s parallax of 9.03 mas, it is located about 360 light-years (110 parsecs) away. The other stars in the system are slightly farther away. Rho Ophiuchi is the namesake of the Rho Ophiuchi cloud complex. It is a nebula of gas and dust, which the Rho Ophiuchi system is embedded in. It is one of the easiest star forming regions to observe, as it is one of the nearest, and it is visible from both hemispheres.

The interstellar extinction of Rho Ophiuchi is measured to be 1.45 magnitudes, meaning the dust and gas in front of Rho Ophiuchi absorbs light from the system, making it appear 1.45 magnitudes dimmer than it should be. Additionally, gas and dust also scatters more higher-frequency light, leaving the light appearing more reddish. The interstellar reddening of Rho Ophiuchi has been measured to be 0.47 magnitudes.

Rho Ophiuchi Nebula - Antares

This is my first processing with material collected in two different sessions, with different exposure parameters. It was a bit of work with it but I have a new skill now 😉


Photos (June 2019) taken at Tenerife, exactly in the place next to “God’s finger”. A great place for astrophotography during night.

Equipment: Canon EOS 6D (no mod!) with a Canon EF 200 [mm] 2.8L II USM lens, on a damaged iOptron CEM 25 mount.

  • Composition: Astro Pixel Processor,
  • Processing: GIMP v2.10.12 + plug-ins (Linux),
  • Lights: 19 x 130[s] ISO 640 + 48 x 60[x] ISO 800,
  • Flats: 40 ISO-640 + 40 ISO-800,
  • Darks: 10 ISO-640 + 19 IS-800,
  • Bias: 20 ISO-640 + 20 ISO-800