Why SO only?As I mentioned for my
Pac-Man image, I have not seen many SO only images, and it was certainly not my initial intent just to do only SO. I had planned, starting in November, to capture duoband SO and then HO images with my color camera, for three targets selected so I could image all night long. I figured by April to be easily done to produce a “wonderful” SHO image of all three targets. However, after going 6 weeks without a single good night over much of the winter, as well as the weakness of the SII signal in these targets, I only will be able to complete the SO part for all three.
Next year I will finish the projects with HO. Meanwhile, I hope you find an SO image interesting.
M42 DetailsThe Orion Nebula, or the Great Orion Nebula, is so well known that it is difficult to know what to say about it. Of course, it is an HII region, an emission nebula, and birthplace of stars.
- At 1,344 light-years away, it is 24 light-years across, with a total mass of 2000 times our Sun.
- It contains the young Trapezium open cluster of 4 stars (well actually six), all in a diameter of 1.5 light-years.
- The nebula was initially known as just the central “star” in Orion’s sword.
- The actual nebulosity was first observed in1610 by Nicholas-Claude Fabri de Peiresc, a French lawyer, subsequently rediscovered over and over again, eventually to be cataloged by Messier.
- In 1865 English amateur astronomer William Huggins using his own visual spectroscopy method, showing M42 was composed of a luminous gas. Initially the spectroscopy forced some to suggest a new element, “nebulium”. However, it turned out that the weird green emission was from a “forbidden transition” for doubly ionized oxygen (OIII), that is one that can occur only under high vacuum, where atomic collisions are rare.
- M42 was the first nebula ever photographed, in an image taken in 1880 by Henry Draper (who is thus the first nebula astrophotographer--yes!!!) with the then new dry plate photography, an 11-inch refractor, and a 51-minute exposure:
My Processing- I calibrated, registered and stacked using DeepSkyStacker.
- I did a background wipe, a bin to 75%, deconvolution, stretching, local contrast and HDR (these latter two modules were critical to handle the dynamic range), and then basic color using StarTools. The star color was done just like one would do HO stars, assuming the SII is picking up red continuum and the OIII picking up green and blue continuum.
- In Photoshop, I separated the stars and nebulosity using StarXterminator for both layers. For the nebulosity layer I used the multi-level unsharp mask of APF-R (used by NASA) for deblurring and NoiseXterminator for noise reduction. For the star layer I did a separate noise reduction. I also did final color, levels and curves adjustments in PhotoShop for both layers, adding the stars on top the nebulosity layer with Linear Dodge (add).
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