The Rosette Nebula (NGC 2237) is one of the most striking emission nebulae in the night sky, but within its vast clouds of ionized gas lies an intricate and lesser-known structure—the "Animal Parade." This central region of the nebula, sculpted by radiation and stellar winds from the open cluster NGC 2244, reveals a mesmerizing collection of shapes that some say resemble creatures marching through space.

For this project, I set out to capture the core of the Rosette Nebula in unprecedented detail using my Celestron EdgeHD 8" with a 0.7x reducer, paired with the ZWO ASI2600MC Pro camera. I imaged from my SkyShed POD observatory— the Kitsilano Observatory—under Bortle 8/9 skies in Vancouver. Over the course of four nights, I collected 21.25 hours of data, using Altair Astro 4nm Ha/OIII and SII/OIII filters to isolate the intricate structures within the nebula. My ZWO AM5 mount provided precise tracking throughout the imaging sessions, allowing me to push deep into the fine details of this celestial masterpiece.

The Gear Behind the Image

Astrophotography requires the right tools to achieve both precision and clarity. Here’s a breakdown of the equipment I used and why each piece played a crucial role:

Telescope: Celestron EdgeHD 8" with 0.7x Reducer

The Celestron EdgeHD 8” (➝ Check Price) is an excellent astrograph for deep-space imaging. With the 0.7x reducer(➝ Check Price), I brought the focal length down to 1400mm at f/7, providing a balance between field of view and resolution—perfect for isolating the Rosette’s core without losing the surrounding nebulosity.

Camera: ZWO ASI2600MC Pro

The ZWO ASI2600MC Pro (➝ Check Price) is a one-shot color (OSC) APS-C sensor camera with excellent quantum efficiency and low noise. Its 16-bit dynamic range helped me capture the fine details of the dark filaments and glowing ionized gas structures in both H-alpha and Oxygen-III emissions.

Filters: Altair Astro 4nm Ha/OIII & SII/OIII

To maximize contrast and detail, I used Altair Astro 4nm dual-narrowband filters (➝ Check Price). The Ha/OIII filter enhanced the dramatic structures in hydrogen and oxygen, while the SII/OIII filter allowed me to double my oxygen data and add sulpher for a true Hubble palette image.

Mount: ZWO AM5 Harmonic Drive Mount

Guiding accuracy was critical for this project, and the ZWO AM5 (➝ Check Price) delivered exceptional stability and tracking with minimal periodic error. At an image scale of 0.55” solid guiding is essential and the AM5 gets the job done in a compact form factor.

My Last Attempt

I recently imaged the Rosette Nebula using my Quattro 150 and was surprised by the detail I was able to capture. I made a crop of the Animal Parade, which was quite nice, but I knew that I had to go back with a larger telescope to take a closer look at those little critters.

Imaging Strategy: Maximizing Detail Over 21.25 Hours

With four nights of imaging, I prioritized long exposure times to enhance signal-to-noise ratio and pull out faint structures in the nebula’s core. Here’s the breakdown of my capture settings:

• Total Integration Time: 21.25 hours

• Sub-exposures: 5-minute frames

• Gain: 100 (Unity Gain)

• Cooling: -10°C

• Filters Used: Altair Astro Ha/OIII and SII/OIII

• Guiding: ASIAIR Pro with Celestron OAG and ZWO ASI174MM Mini

By integrating over 20+ hours, I was able to reveal the subtle textures of the Animal Parade, showcasing details that are often lost in shorter exposure images. I usually like to shoot twice as much data with the SII/OII filter because those emission lines are much weaker than hydrogen alpha, but the weather is always a factor. I was able to capture two nights with each filter for a pretty even mix. The Rosette Nebula is very bright, so it ended up being enough data to make a solid image. With the f7 focal ratio of this telescope, the more data I can accumulate, the better. I typically aim for 30 hours, but rarely reach that target to to the weather here in the Pacific Northwest.

Processing Workflow: Bringing the Animal Parade to Life

After acquiring the data, I processed the images using Astro Pixel Processor, PixInsight and Photoshop, applying a workflow designed to enhance structure while maintaining a natural aesthetic:

1. Preprocessing (Calibration & Stacking)

   • Used the extract Ha and OIII debayer algorithms in APP to get individual hydrogen alpha, oxygen iii, and sulphur ii monochrome images

   • Applied dark, bias, and flat frames for calibration. The ASI2600MC Pro lacks amp glow, so flat darks are not necessary

2. Linear Processing

   • Seti Astro Auto DBE script to remove gradients

   • Deconvolution for sharpening fine details with BlurXterminator

   • Noise reduction using NoiseXterminator

   • Star removal with StarXterminator

3. Non-Linear Processing

   • Generalised Hyperbolic Stretch to reveal nebular detail

   • Pixel Math colour combination and balancing using the Hubble Palette (SHO)

   • Sharpening with Local Histogram Equalization and Unsharp Mask

   • Final adjustments in Photoshop for contrast, colour adjustment, and sharpening

Final Thoughts: Why I Love This Target

The Rosette Nebula’s core is a challenging yet rewarding target, offering incredible detail and depth for those willing to invest time in capturing and processing it. With the right gear and techniques, you can reveal its hidden structures—even from a light-polluted city like Vancouver.

If you're looking to take your astrophotography to the next level, I highly recommend exploring narrowband imagingand investing in high-quality filters, precise tracking mounts, and cameras with excellent dynamic range. Want to get started? Check out some of my recommended gear below:

✅ Celestron EdgeHD 8" with 0.7x Reducer ➝ Check Price
✅ ZWO ASI2600MC Pro Camera ➝ Check Price
✅ Altair Astro 4nm Filters ➝ Check Price
✅ ZWO AM5 Harmonic Drive Mount ➝ Check Price

Have you imaged the Rosette Nebula? Share your experiences in the comments below! And if you found this post helpful, consider subscribing to my YouTube channel where I break down astrophotography techniques and share behind-the-scenes insights from the Kitsilano Observatory.

Clear skies and happy imaging!

Rob