- Date: January 2017
- Location: Eggersdorf, Germany
- Camera: Atik383L+
- Optics: 10″ f/4 TS ONTC Newton
- Filters: Astronomik Ha 6nm, OIII 12nm, SII 12nm, R
- Exposure: Ha 12 x 1800 1×1, OIII 14 x 1200 1×1, SII 14 x 1200 1×1, R 8 x 300 1×1
Frank Iwaszkiewicz has taken this image of this seldom imaged nebula in Orion. SH2-261 takes its name from the Sharpless catalogue of emission nebula. This nebula is also known as Lowers Nebula, as it was discovered by Harold Lower and his son Charles from photographic plates taken with their homemade 8 inch F/1 Schmidt camera in 1939.
Using Narrowband filters, Frank was able to capture the photons from the Sulphur 2, Oxygen 3 and Ha, emission lines of light. Atoms in the nebula become excited from stellar radiation. The energy is absorbed by the atoms, and their electrons gain energy and move into higher energy levels. These higher levels are unstable and the electron falls back into their stable lower energy state. As they fall back to the lower state, they emit the energy difference between states as a quantum of energy.
This energy corresponds to a wavelength which can be imaged through these narrowband filters as they are tailored to block all other wavelengths and pass the specific light of the emission nebula.
In Franks image, he used the 3 filters to make a Hubble palette, which he combined with two versions of a Bi-Colour image, to create his final colour blend. This was taken with a 200mm F/4 Newtonian telescope.
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