How My Mosaic Image of the Veil Nebula Was Created – A Night Under the Stars

Astrophotography is more than just capturing beautiful objects in the night sky. It's a process that requires planning, technical precision, patience, and a good dose of passion. In this post, I’d like to take you along on one of my most exciting sessions yet: capturing a mosaic image of the Veil Nebula, a vast supernova remnant located in the constellation Cygnus.

From Idea to Plan

As with most of my projects, everything started with an idea on my phone. I wanted to capture the entire Veil Nebula in high resolution – including the Eastern and Western Veil as well as Pickering's Triangle. Since the object is too large to fit in a single frame with my telescope, I planned a mosaic of four panels that would later be stitched together.

Using apps like Stellarium and the ASIAir app, I mapped out the mosaic field, defined the shooting order, and calculated the best observing times. The perfect window was a clear, moonless night with stable weather.

The Equipment – Compact but Thoughtfully Assembled

For this project, I used my trusted mobile astrophotography setup:

• Telescope: Celestron RASA 8" (f/2) – extremely fast and perfect for short deep-sky exposures.

• Primary Camera: ZWO ASI 2600MC Pro – cooled, excellent dynamic range, perfect for color imaging.

• Backup Camera: ZWO ASI 183MC Pro – just in case, in case a cable is missing or there’s a hardware issue.

• Mount: Skywatcher AZ-EQ6 Pro – precise and stable for long sessions.

• Control & Guiding: ASIAir Plus, ZWO EAF focuser, and a ZWO mini guide scope with guide camera.

• Accessories: Power cables, USB hubs, various adapters, a light panel for flat frames, tools, and spare parts.

• Power Supply: A powerful portable lithium battery.

Everything was carefully packed into the car. Once you’re out in the field, especially in a remote area, forgetting a single item can ruin the entire night.

Setup Under the Night Sky

My destination was a quiet parking lot near Saland, in the Zürcher Oberland, away from any street lights. A peaceful place near the edge of a forest with a wide view of the sky – perfect conditions.

The setup followed a well-practiced sequence:

1. Mount roughly aligned to true north.

2. Telescope mounted, camera attached, cables connected.

3. Battery connected, system powered up.

4. Mount balance checked – especially important with the heavy front of the RASA.

5. Focusing using the electronic ZWO EAF.

6. Polar alignment via the ASIAir app:

The camera takes two slightly offset sky images. The app then calculates how far the azimuth and altitude screws need to be adjusted to align with the celestial pole.

After alignment, I captured a test image (60s exposure) to check star shapes and field flatness. The focus was spot on, stars were round, and the RASA 8 delivered its famously flat field – an important factor when stitching together a mosaic.

The Capture – Four Panels, One Vision

Once everything was aligned and focused, I started the guiding calibration. Since the mount had been freshly set up, the guider needed to recalibrate to avoid tracking errors.

Then the scope slewed to the first mosaic panel – and the Veil Nebula was perfectly framed on the first try.

Each panel consisted of around 60 exposures at 60 seconds each – resulting in about four hours of total exposure time. While the telescope was shooting, I periodically checked the system, but for the most part, I rested in the car.

Morning Routine – Checking & Calibration Frames

Around 4:00 AM, shortly before sunrise, I got up to inspect the results. Everything had held up beautifully – focus still perfect, no dew on the optics, tracking stable.

Next, I took the calibration frames, which are essential for high-quality processing:

• Flat frames: Captured with a flat panel just before dawn, to correct for vignetting and dust.

• Dark frames: I used a pre-built dark library stored on my PC. However, they must match exactly in exposure time, gain, cooling temperature, and even focus position to be valid.

If any of these values differ, the darks won’t apply correctly during stacking and calibration.

Processing at Home – The Other Half of the Work

Back at home, I transferred the data from the ASIAir to my PC and started the post-processing phase.

Stacking with DeepSkyStacker:

• Lights, flats, and darks were imported.

• Roughly 10% of the images were rejected due to guiding errors, satellite trails, or motion blur.

• Result: Four clean, stacked images – one for each mosaic panel.

Image Processing in PixInsight – Turning Four Into One

With the stacks ready, I moved on to PixInsight, the powerhouse for astrophotography processing:

1. Rotation & Plate Solving – The RASA outputs mirrored images, so I first had to rotate them before using plate solving.

2. Alignment – The panels were aligned using astrometric data.

3. Gradient removal & background neutralization – Tools like DBE or GradientXTerminator helped clean up the field.

4. Cropping – Edge artifacts from stacking were removed.

5. Mosaic merging – With tools like GradientMergeMosaic, I blended the four panels into a seamless image.

6. Noise reduction – Using NoiseXTerminator to smooth background noise while preserving detail.

7. Detail enhancement – BlurXTerminator helped sharpen and refine structures.

8. Star removal – Using StarXTerminator, I separated the stars from the nebula for separate editing.

9. Nebula enhancement – Boosting contrast, structure, and color using Histogram Transformation, Curves, and masks.

10. Star editing – Adjusting star color, size, and brightness separately.

11. Final recomposition – Merging the starless nebula with the processed stars for a balanced final image.

As a final touch, I often bring the image into Adobe Lightroom to fine-tune colors, clarity, and brightness.

The Result – A Piece of the Universe in Four Parts

The finished image reveals the Veil Nebula’s intricate filaments, soft transitions, and rich colors. It’s the product of:

• Hours of preparation

• Technical precision

• A long, calm night in the field

• And a deep fascination with the sky

I usually share the final image on my social media channels and upload it to my website/shop, where it’s available as a high-quality print.

Conclusion – More Than Just a Picture

Creating this mosaic of the Veil Nebula was one of my most rewarding astrophotography projects. It shows just how deep this hobby can go – beyond the telescope, into the world of data, software, image processing, and artistic interpretation.

If you have questions about my gear, PixInsight workflow, or mosaic capture techniques – feel free to reach out!
Until then: Clear skies and beautiful nights!

If you'd like, I can also help you create a shortened version for Instagram, a header for your website, or a technical guide for PixInsight mosaics. Just let me know!