216 Hours on Andromeda — A Team, A Gamble, A Galaxy Revealed

Capturing the Andromeda Galaxy is not uncommon.
Resolving it—star by star, across its vast spiral arms—is something else entirely.
For the four-member team Cosmic Quadrant, this project became a test of patience, precision, and collaboration. Over nearly six months, they combined time, technology, and shared vision to produce a 216-hour long focal-length mosaic of M31—revealing details rarely seen at this scale.

© Cosmic Quadrant：Yuchu Hong, Yaguang Wan, Jingyao Hong, and Xi Zhu

Who Is Cosmic Quadrant?

Cosmic Quadrant is a four-member astrophotography team consisting of Yuchu Hong, Yaguang Wan, Jingyao Hong, and Xi Zhu.
Among them, Xi Zhu stands out as a highly experienced astrophotographer, well-known within the community and often invited as a judge in competitions. His deep passion for both astronomy and imaging, along with his constant sharing of techniques and insights, played a crucial role in bringing this M31 project to completion.
Without his involvement, the team admits, the project might have stretched well into the following year.

How It All Began

The team was originally formed at the Daocheng Observatory in Sichuan, where Yuchu Hong initiated the idea of assembling a group for a large-scale collaborative project.
What started as four strangers quickly evolved into a tightly coordinated team.
“We came together for one ambitious project—and somewhere along the way, became true teammates.”
The M31 project began in August 2024, with active data acquisition lasting nearly four months, followed by an additional two months of processing and post-production.
Nearly six months later, the 216-hour mosaic was complete.

Why M31?

The inspiration came from a striking image taken with a 1-meter telescope, showcasing the NGC 206 region of M31 with exceptional clarity—resolving individual stars deep within the galaxy.

That raised a question:
Could smaller telescopes—10 to 12 inches in aperture—achieve something similar through sheer exposure time?
In late August 2024, the first test was conducted using a 12-inch telescope.
With just 5 hours of luminance data, the result already hinted at extraordinary potential.
That was the turning point. If one region could reach that level of detail… what if the entire galaxy could be captured the same way?

The Equipment Behind the Image

To resolve the finest details in M31, the team relied on a set of large-aperture, long focal-length systems:

• Three RC telescopes from GSO (two RC12, one RC14)
• One 12.5-inch AG telescope
• All paired with ZWO ASI6200MM Pro full-frame cameras
• A mix of 2-inch and 50mm filters from different brands
  For wide-field gradient calibration, Wan used a Takahashi E160ED (160mm aperture, 535mm focal length) to collect broadband reference data.

Where the Data Was Captured

Location played a crucial role.

• Four systems were deployed in Daocheng, Sichuan, at elevations above 3,800 meters under dark skies
• An additional setup was operated at the Lijiang Twin Observatory
  These conditions allowed the team to push for deep exposure and high signal quality.
  

What Makes This M31 Stand Out

When asked what viewers should focus on, the answer is clear:
“This is one of the first successful long focal-length mosaic M31 projects at this scale—8 to 9 panels—completed in both the AstroBin.”
But more importantly, it’s about the level of detail.

• Individual stars are resolved across the spiral arms
• Dense regions near NGC 206 show fine structure
• Even the faint outer regions—often seen as diffuse haze—are clearly broken into discrete stars
  Beyond resolution, the team also explored combining H-alpha data with luminance to reveal subtle structural features in the galaxy’s core.
  “We didn’t have enough Ha data for a full result, but the effect is there.”

The Biggest Challenge: A Broken Background

The hardest part didn’t come during imaging—it came during processing.
In the linear stage, after assembling the RGB mosaic, the team encountered severe issues:

• Strong, inconsistent background gradients
•  Visible seams between panels
• Large-scale variations caused by differences in optics, filters, angles, and shooting conditions
  “The background looked terrible. It was the biggest problem we faced.”
  And by then, it was already December.
  M31 was too low in the sky to start over.

A Risky Decision

With no option to reshoot, the team had to find a solution.
“As the one who initiated the project, I had no choice but to keep pushing forward.”
After extensive searching, they identified a complex and rarely used technique:

Multi-Scale Gradient Correction (MSGC)

This method—later integrated into PixInsight as part of the MARS project—became the key.
Using wide-field reference data captured with the Takahashi E160ED, they were able to correct the gradients and complete the mosaic.

The Hidden Work: Data Selection

Another major challenge was data selection.

• Over 300 hours of data were initially captured
• After filtering, only 200+ hours remained
  Each frame had to be reviewed—both automatically and manually.
  “It’s extremely time-consuming, but necessary.”
  From a practical standpoint, the team notes that the cost of time and equipment for this single image reaches into five figures.
  They also mentioned they are open to sharing a JPEG version for others interested in processing such rare, high-integration data.

Technical Q&A: Gradient Removal

A user asked about struggling with background gradients in Siril.
The team’s advice:

• Start with DBE (Dynamic Background Extraction) in Siril
• If needed, try PixInsight tools such as the Seti Astro suite
• If the data is too difficult, consider switching targets or using dual narrowband filters
  “In theory, it’s solvable. I’ve even managed gradients shooting the Milky Way core from downtown Guangzhou using proper DBE parameters.”

Technical Q&A: Creating Super Luminance (Super L)

Two approaches were shared:
Method 1 (Simplified)

• Generate master frames using WBPP
• Duplicate files to meet PixInsight’s Image Integration requirement (>6 inputs)
• Integrate without rejection to produce a Super L frame

Method 2 (Advanced)

• Integrate all calibrated and aligned single frames (L + RGB)
• Produces higher quality, but extremely time-consuming
  “We don’t generally recommend the second method unless you really need it.”

Advice for Beginners

When asked what they would say to newcomers, the answer was refreshingly honest:
“Before astrophotography, nightlife meant holding a drink. Now it means carrying telescopes.”
They encourage more people to join the hobby—but acknowledge the learning curve.
While this project represents the high end of collaborative astrophotography, the team emphasizes that the journey into astronomy doesn’t have to begin this way.
Accessible tools—such as Seestar smart telescope—are making it easier for more people to take their first step.
By simplifying setup and reducing technical barriers, systems like Seestar allow beginners to focus on the experience itself: capturing their first image, understanding the sky, and building confidence.
From there, more advanced systems can follow naturally.

More Than Just an Image

For the team, astrophotography is not only about results—it’s about the process.

• The satisfaction of capturing data
• The challenge of processing
• The friendships built along the way
  “We went from strangers to close teammates through this project.”
  They also believe more outreach and education could help grow the community, making astrophotography more accessible to newcomers.
  Tools like Seestar, they note, help lower the entry barrier—allowing more people to experience the joy of astronomy before moving into more advanced setups.

A New Way to Shoot the Sky

As more astrophotographers explore collaborative workflows and integrated systems, projects like this point toward a broader future—one where precision, accessibility, and shared effort come together.
“Astrophotography doesn’t have to be a solo effort.”
By combining:

• Similar equipment
• Shared field of view
•  Collective exposure time
  They were able to achieve something far beyond what a single setup could produce.
  “When you work together like this, 1 + 1 becomes greater than 2.”