Edit 2/11/2023: This image was featured by NASA’s universe view screen Instgram, Astronomy Magazine’s image of the day: https://astronomy.com/photos/picture-of-day/2023/02/a-wide-view-of-orion, and the Amateur Astronomy Image of the Day: https://www.aapod2.com/blog/M42
The dark Horsehead Nebula and the glowing Orion Nebula are contrasting cosmic vistas. Adrift 1,500 light-years away in one of the night sky’s most recognizable constellations, they appear in opposite corners of the image. The familiar Horsehead nebula appears as a dark cloud, a small silhouette notched against the long red glow at the lower left. Alnitak is the easternmost star in Orion’s belt and is seen as the brightest star to the left of the Horsehead. Below Alnitak is the Flame Nebula, with clouds of bright emission and dramatic dark dust lanes. The magnificent emission region, the Orion Nebula (aka M42), lies at the upper right. Immediately to its left is a prominent reflection nebula sometimes called the Running Man. Pervasive tendrils of glowing hydrogen gas are easily traced throughout the region.
This is easily one of my most ambitious astrophotography projects to date. Given that I’m fairly limited by my dslr in terms of imaging very dim objects, I decided to dump as much time on Orion as possible to see how much dust and gas in the region I could reveal. I was struck by how much wispy H-alpha gas didn’t line up exactly with the dust in the region – it was very cool to see the differences in ionized and non-ionized gas.
Image:
You can find a full quality version here: https://live.staticflickr.com/65535/52676069217_9f55ac7dd5_o.png
Annotated Image:
Equipment:
- Nikon D800
- 200mm F4 lens
- GEM 28
- NINA
- Nikonhacker
Acquisition
- ISO 800, F4
- Taken from a bortle 1 zone in Northwest CT
- 1240 x 180s (62 hours) – Taken on 12/18/2022, 12/20/2022, 12/21/2022, 12/22/2022, 12/23/2022, 12/24/2022, 12/27/2022, 1/18/2023, 1/21/2023, 1/22/2023, 1/23/2023. 1/24/2023
Processing:
Pre-processing and stacking
- All subframes were calibrated and normalized through WBPP
- The subframes were debayered and split into monochrome channels
- The subframes were registered with distortion correction
- the subframes were registered based on a PSF snr estimate
- The subframes were normalized using local normalization
- Each channel was integrated separately using the linear fit clipping algorithm
- all the channels were integrated together using the ESD clipping algorithm
Preparation of all frames:
- Stacking artifacts were cropped
- the RGB channels were combined to create an RGB image
- the RGB image was plate solved
- DBE was applied iteratively
- the RGB image was photometrically color calibrated
Deconvolution of the luminance
- a PSF was created using the dynamic PSF process
- Linear starnet was applied
- The starless image was deconvoluted
- the stars were added back in
Linear noise reduction
- A low-contrast mask was applied
- Two iterations of TGV noise reduction were applied, one targeting high-frequency noise and one targeting low-frequency noise
- A medium-contrast mask was applied
- MMT targeting all 8 scales was applied to remove large-scale noise
Stretching
- the luminance image was stretched using GHS
- the RGB image was stretched using Arcsinh stretch
Non-linear adjustments:
- The stars were separated from the nebula using Starnet 2
- The RGB image was stretched using Arcsinh stretch
- LRGB combination of starless images
- HDR, LHE, and curves to increase local contrast
- Saturation was increased
- MLT was applied targeting 5 layers of luminance
- The image was relinearized and the stars were added back
- The background level was set to .09