This image marks the final deep-sky project captured with my ZWO ASI585MM Pro before moving to a larger-sensor camera — a fitting subject to close out that chapter.

The Horsehead Nebula (Barnard 33) lies about 1,300 light-years away in the constellation Orion, silhouetted against the glowing hydrogen of IC 434. The dark “horse” shape is a dense pillar of dust and gas being slowly eroded by nearby massive stars. Just below it sits NGC 2023, a bright blue reflection nebula, making this region a striking example of both stellar formation and destruction within the Orion Molecular Cloud Complex.

Rather than pushing total integration time, this project focused on data quality and dynamic range, using a mixture of exposure lengths to manage the bright regions around Alnitak while still pulling out faint dust and hydrogen structures. The final image combines Luminance and H-alpha with RGB data: H-alpha to add punch to the emission regions, and Luminance to enhance the fine dust detail throughout the frame.

Processing Notes

I loosely followed the RGB4B – LHa-RHaGB workflow, but struggled most with continuum subtraction. Balancing H-alpha without overwhelming the natural RGB signal — especially near reflection regions — is an area I’m still refining. For this image, I chose a more restrained blend, prioritizing smooth transitions and natural color over aggressive separation.

This felt less like a finale and more like a quiet milestone. The ASI585MM Pro has been a fantastic camera to learn mono imaging and narrowband blending — and it seemed only right to end its run with one of the most iconic and challenging regions in the night sky.

Clear skies 🌌