NGC 891: The Silver Sliver Galaxy

This month, we're diving into the mesmerizing beauty of NGC 891, also known as the Caldwell 23 galaxy. This celestial object is a fantastic example of an edge-on unbarred spiral galaxy, presenting itself to us like a delicate, silvery sliver against the vast canvas of space.

Located approximately 30 million light-years away in the constellation Andromeda, NGC 891 boasts an impressive size in our night sky, measuring about 13.5 by 2.5 arcminutes. Its nearly perfect edge-on orientation allows us to peer directly through its dusty disc, revealing intricate details of its spiral structure and the bright core.

Capturing the Sliver

Achieving a clear view of galaxies like NGC 891 can be a challenging endeavor, especially when the bright light of a full moon interferes with sensitive deep-sky imaging. This particular capture was made with the photographer noting the primary limitation of noise due to the proximity of the full moon, a valuable reminder for fellow astrophotographers to plan galaxy shoots during darker phases of the moon.

Here's a breakdown of the technical details behind this stunning image:

• Integration Time: 127 frames of 60 seconds each, totaling 2 hours and 7 minutes of exposure.
• Filter: None, utilizing a broadband unfiltered approach.
• Sky Quality: Bortle 4, indicating a relatively dark sky.
• Camera: Sony a6400 (unmodified).
• Telescope: Celestron NexStar 8SE, used with a focal reducer.
• Mount: NexStar SE Alt-Az mount, configured with an EQ wedge.
• Guiding: ZWO ASI120MM Mini camera paired with PHD2 software for guiding stability.
• Acquisition & Processing Software: NINA was used for image acquisition, Siril for stacking and calibration, and Photoshop for the final color adjustments and detail enhancement.

Processing Workflow

The processing journey involved several key steps to bring out the best in the captured data:

• Calibration and Stacking: Raw frames were meticulously calibrated using dark, flat, and bias frames within Siril.
• Image Enhancement: Techniques like background extraction, color calibration, and histogram stretching were applied to optimize the image's dynamic range and color balance.
• Detail Refinement: Subtle saturation adjustments were made to highlight the delicate dusty lanes and the luminous galactic core, bringing the Silver Sliver galaxy to life.

NGC 891 is a testament to the wonders of the universe that await our observation, and with careful planning and execution, even challenging conditions can yield breathtaking results.