Processing story / Iris Nebula NGC 7023
Finding the detail in the dust
A blue core, a field of faint dust, and the choices that brought them together. Follow one image from separate monochrome channels to the final LRGB blend.
Photography and processing by Michael Page
- LRGB exposure
- 31 h 20 min
- Light frames
- 376
- Per exposure
- 300 s
- From capture to stars
- 6 stages
Let the dust tell the story.
The bright center was only part of the picture. The challenge was to reveal the surrounding dust without letting the core wash out or the stars take over. Processing the color, luminance, and stars separately gave each part of this image the attention it needed.
The pivotal decision was to combine detail from luminance with color from RGB, then finish the core and stars independently.
See the difference
Two decisions, made visible
What luminance brought to the dust
Compare the saved starless RGB with the saved starless LRGB version.
Drag the arrows on the image to compare. You can also use the arrow keys when the handle is selected.
Saved processing stages, shown without an additional stretch or brightness matching. This compares the versions as a whole, not an isolated single-setting experiment.
The final layer of stars
See how the star field changes the same composition.
Drag the arrows on the image to compare. You can also use the arrow keys when the handle is selected.
Both exports use the same framing and display conversion. Move the divider to compare the saved starless and final masters.
At the telescope
- Telescope
- William Optics UltraCat 108
- Camera
- ZWO ASI2600MM
- RGB filters
- Astronomik
- Camera settings
- Gain 100 · Offset 50 · −5°C
- Exposure length
- 300 seconds per frame
- Processing
- PixInsight
| Channel | Frames | Exposure |
|---|---|---|
| Luminance | 155 | 12 h 55 min |
| Red | 75 | 6 h 15 min |
| Green | 73 | 6 h 05 min |
| Blue | 73 | 6 h 05 min |
| HαEvaluated separately | 30 | 2 h 30 min |
The final image uses LRGB. The additional 2 h 30 min of Hα is excluded from this version.
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