Astrophotography Stacking

While you will learn lots about computational photography and how you can process many images together to produce a single much cleaner, more detailed and less noisy file, this lesson is quite specific to astrophotography. It can be great fun, but if you’re not interested in the stars, or the colourful almost abstract images you can create with them, feel free to skip this section.

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Key points

1. You can utilise dedicated astrophotography stacking features in software (e.g., Affinity Photo) to combine multiple light frames with calibration frames for improved image quality.
2. Stacking workflow – use the Astrophotography Stack Persona to load light frames and calibration frames (bias, darks, flats).
3. Stacking options – Sigma clipping is the best default; it removes outliers like satellite or aircraft trails.
4. Raw options – leave Bayer pattern inferred unless colours are wrong; “Master Flat” can correct green bias.
5. After stacking, the image opens in the main Photo Persona for editing.
6. Initial tone stretch – apply Levels and Curves to reveal faint detail.
7. Brightness/contrast with blend ranges – lifts the image without blowing out highlights.
8. Remove background cast – Filters → Astrophotography → Remove Background, sample clear area, adjust black level.
9. Clarity filter with blend ranges – enhances structure while protecting highlights.
10. HSL adjustments – selectively enhance the saturation and luminosity of specific colour ranges, such as reds, yellows, and cyans to bring out nebula and star colours.
11. Final brightness/contrast tweak gives extra tonal punch.

View the transcript on YouTube: Open video, then ••• → Show transcript

• Remember to collect enough calibration frames (bias, darks, flats) for best results – the demo assumes these are available.
• Overusing Clarity or Contrast can make stars look unnatural; apply gently.

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Extra Thoughts

1. Astrophotography stacking, while specific to a genre, is an excellent example of advanced digital manipulation and enhancement techniques that demonstrate a high level of technical and creative skill in post-production.
2. It falls under the SQA requirement for “exploring and experimenting with a range of photographic media, manipulation techniques and processes”.
3. The process involves combining multiple images (light frames, along with calibration frames like bias, darks, and flats) to improve image quality by reducing noise, increasing detail, and extending the dynamic range, which is often crucial for revealing faint celestial objects.
4. Techniques used in astrophotography stacking, such as tone stretching (Levels/Curves), brightness/contrast adjustments with blend ranges, background cast removal, clarity enhancement, and HSL adjustments for colour saturation, are applicable to other forms of digital manipulation and demonstrate a sophisticated understanding of image editing.
5. Therefore, even if astrophotography is not your chosen project topic, understanding the principles and processes of image stacking showcases your ability to apply and experiment with complex post-production techniques to achieve a desired visual effect and technical competence. This can contribute to demonstrating a strong understanding of photographic practice.

Note - ToDo

While this is a section on Post Production, which brilliantly illustrates semi-manual computational photography, to do the exercise, we are going to have to provide some additional training on creating the files required for it.

Exercise

1. Determine if you can safely manage an astrophotography shoot. We would advise against it unless you can be accompanied by a trustworthy adult. If you can:
2. Plan a time at a dark sky location when there will be clear skies, ideally no moon.
3. After shooting your light frame remember to shoot dark frames, bias frames and flat frames.
4. Process as per the video above.
5. Write about your experience, was the final file worth it? Write down any lessons you learned. Given your leaning might your next astro image be even better?