Rho Ophiuchi Cloud Complex Captured with a Smartphone: An Untracked Astrophotography Feat

Astrophotography often conjures images of massive telescopes and sophisticated tracking mounts. However, a recent achievement demonstrates that with the right dedication and techniques, even a smartphone can capture the wonders of the night sky. This post delves into the creation of a captivating image of the Rho Ophiuchi Cloud Complex, shot entirely with a Xiaomi 13T.

The Gear and the Challenge

The image was captured using a Xiaomi 13T, specifically its 50 mm (2x) telephoto lens, powered by an Omnivision OV50D40 sensor. The shooting parameters were: F/1.9 aperture, ISO 1600, and an 8-second exposure.

The primary challenge for this astrophotographer was the absence of a star tracker. This meant that without tracking the apparent motion of the stars, long exposures would quickly result in star trails. To overcome this, approximately 1204 frames of luminance (L) and 850 frames of data for color (likely RGB) were captured. This necessitated reframing the tripod a staggering 17 times over the course of four different nights to maintain the target in the frame.

The Processing Pipeline

Capturing the data is only half the battle in astrophotography. The post-processing is where the magic truly happens, especially when dealing with the artifacts inherent in untracked and manually reframed shots.

The raw frames were stacked using Sequator, a popular free software for stacking astronomical images, particularly useful for handling untracked sequences and mitigating noise. The stacking process helps to improve the signal-to-noise ratio, bringing out fainter details.

Following stacking, Siril was employed for a series of crucial processing steps:

• Green Noise Removal: Essential for cleaning up the common green tint often seen in stacked images.
• Color Calibration: Ensuring accurate and natural colors for the nebula and stars.
• Background Extraction: Removing the gradient from light pollution and enhancing the contrast of the target.
• Starless Stretch: Applying a stretch to bring out the details in the nebula without blowing out the stars.
• Star Recomposition: Carefully reintegrating the stars after the stretch, often a critical step to avoid artifacts.

Finally, Lightroom Mobile was used for the "final touch up," likely involving adjustments to overall contrast, saturation, and sharpening to give the image its polished look.

Results and Takeaways

Despite the limitations of an untracked setup and the demanding nature of reframing, the resulting image of the Rho Ophiuchi Cloud Complex is remarkably detailed and colorful. The deep reds and blues of the nebula, along with the intricate dust lanes, are clearly visible. The photographer's skill in both capture and processing is evident, showcasing what's possible with modern smartphone cameras and dedicated effort.

This achievement is a testament to the evolving capabilities of smartphone technology and the ingenuity of astrophotographers in pushing the boundaries of what's possible, even under challenging conditions. It's a great inspiration for anyone looking to start their astrophotography journey with minimal equipment.