Capturing the Majestic M31: A Deep Dive into Andromeda Astrophotography

The Andromeda Galaxy, also known as M31, is our nearest galactic neighbor and a breathtaking target for astrophotographers. This post delves into the process of capturing and processing a stunning image of this iconic celestial object, offering insights into the equipment, techniques, and dedication required.

The Cosmic Canvas: Acquisition Details

This image of M31 was captured on August 22, 2025, under the pristine conditions of Bortle class 4 skies. Bortle class 4 skies are known for their low light pollution, allowing for the capture of fainter details in deep-sky objects.

The imaging session comprised a total of 24 x 2-minute exposures, resulting in a combined exposure time of 48 minutes. To ensure the highest quality data, 10 dark and 10 bias calibration frames were also collected. Calibration frames are crucial in astrophotography for removing noise and correcting for sensor imperfections.

Equipment and Settings:

• Camera: Canon EOS T7
• Lens: Sigma 150-600mm f/5-6.3 Contemporary
• Mount: Sky-Watcher Star Adventurer 2i
• Focal Length: 300mm
• Exposure: 30 x 121” subs, with 24 suitable for stacking.
• ISO: 1600
• Aperture: f/5.6

These settings were chosen to balance image detail, signal-to-noise ratio, and the capabilities of the equipment under the specific sky conditions.

Bringing the Galaxy to Life: Post-Processing Workflow

Post-processing is where the magic truly happens in astrophotography. The collected light and calibration frames were stacked using Deep Sky Stacker (DSS). This process combines multiple exposures to significantly improve the signal-to-noise ratio and bring out faint details.

The resulting 16-bit file was then imported into Adobe Photoshop for further refinement. A meticulous series of adjustments were made to enhance the galaxy's features:

• Curves and Levels: These adjustments were used to reveal the subtle details within the galaxy and establish the black and white points. A "dark threshold layer" was employed for precise black and white point setting.
• Color Correction: Color balance adjustments and color range selections were made to accurately represent the galaxy's natural colors.
• Detail Enhancement: A high-pass filter was applied to accentuate the intricate dust lanes that weave through M31's spiral arms.
• Further Adjustments: Multiple rounds of curves and levels adjustments were performed to fine-tune the overall appearance.
• Camera Raw Filter: Minor adjustments to exposure, clarity, dehaze, and highlights were made using the Camera Raw filter before exporting as a PNG.
• Lightroom: The image was then opened in Adobe Lightroom for final tweaks, including the application of a radial gradient filter to adjust exposure, highlights, and white balance of the galaxy, as well as cropping.
• Denoise AI: Finally, the image was processed with Denoise AI, utilizing a custom sharpen/denoise setting to further refine the details and reduce any remaining noise.

This detailed post-processing workflow is essential for transforming raw astronomical data into a visually stunning representation of the universe.