An SO image for nowI have not seen many SO only images, and it was certainly not my initial intent. My actual intent was, starting imaging in December, to capture duoband SO and HO images with my color camera. I figured by March to be easily done to produce a “wonderful” SHO image. However, going 6 weeks without a single good night, as well as the weakness of the SII signal meant that I have had to abandon the HO for now. I decided to work the SO data up and see how it looked. Next year I promise to finish the project with HO.Some good things came out of this.
- The SII came out well, despite the faint SII signal. Had I seen [url=http:// https://www.galactic-hunter.com/post/ngc-281-the-pacman-nebula]“Galactic Hunters” image[/url] first, I would not have started this in SO, as the SII is so very weak compared to OIII, which in turn is weak compared to the dominant Ha.
- Unlike an SHO image, it is really clear here how SII contributes, as color mapping is simple: Red is SII while Blue and Green are OIII.
- I was super happy with the detail: with just SII and OIII there is no dominant Ha that overwhelms.
The Pac-Man Nebula: What’s in a name?I presume many are familiar with Pac-Man character, the video game “icon” that eats the power pellets and ghosts. Iwatani at Namco designed the Pac-Man (Puck Man in Japan) in the shape of a pizza with a missing slice, but also as a morph of the Japanese character “kuchi” 口 (which means mouth). I’m old enough to remember the excitement of the game coming out and playing it in the early 80’s.
Nebula descriptionThe Pac-Man is an emission nebula and HII region, also known as NGC 281, IC 11 and Sh2-184, and is a part of our Milky Way's Perseus Spiral Arm, 9200 light years away.
- Associated with the nebulosity is the “young” 3.5-million- year-old open cluster IC 1590 (Collinder 8).
- The open cluster also includes the quintuple O-type star system near the centre, which creates the ionization and fluorescent glow of the nebula.
- The nebula contains the awesome dust lane that is the mouth of the Pac-Man. As far as I know this dark rift has no independent designation, but if anyone knows please let me know.
- The nebula also contains Bok Globules, which are the dark knots of dust and gas, nicely visible in my image. Below is a close-up from my image:
- But for an amazing close-up, the HST image cannot be beat, you can find it here: https://science.nasa.gov/image-detail/hubble-nebula-bok-display/
- These globules can be the birthplace of stars, before the globules ultimately dissipate.
- Finally there are some wonderful pillars of cold dust and gas to the left side, which will ultimately be eaten away by the UV radiation and stellar winds from that central stellar multiplet.
Processing- I calibrated, registered and stacked using DeepSkyStacker
- I did a background wipe, a bin to 66% of the captured image, deconvolution, stretching and basic color using StarTools. The stretch was done twice, once for the nebulosity and once for the stars. I did the star color as 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 in both layers using StarXterminator. For the nebulosity layer I used the multi-level unsharp masking in APF-R (used by NASA) for deblurring and NoiseXterminator for noise reduction. I also used Camera Raw for a slight sharpening and color noise reduction. I did final color adjustments in PhotoShop for both layers, adding the stars on top with a Screen function.
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