What Is Post-Processing in Astrophotography and How Does It Work?

Post-processing is the “art” of turning raw astronomical data into vivid color images. It’s where your creativity and skills shine, allowing you to craft unique, breathtaking representations of the cosmos.

If you're just getting started or want to refine your skills, check out our tutorial "The Art of Post-Processing" for step-by-step guidance from Telescope Live’s expert astrophotographers.

While it’s possible to produce a great-looking image in just a few minutes, mastering every aspect of the data to create truly stunning pictures often takes practice and patience. The key lies in understanding your data and learning how to use the right tools effectively..

The raw images you process are a collection of individual frames of the same deep-sky object. These frames, captured using high-precision telescopes and cameras, are available for download through your Telescope Live subscription.

Each frame is captured with a specific filter, such as Red, Green, or Blue, and saved in the FITS format—a file type commonly used in astronomy.

FITS (Flexible Image Transport System) is the standard file format for astronomical data. Unlike JPEGs, which are compressed to save space at the cost of resolution and detail, FITS files are uncompressed and preserve every bit of information captured by the telescope.

Key facts about FITS files:

Each FITS image has an associated exposure time, which is the duration for which the camera shutter remains open. Common exposure times range from 5 to 10 minutes.

To produce a high-quality astrophotography image, you’ll need several hours of total exposure time. However, rather than capturing this in a single shot, the total time is divided into multiple frames. These individual images are then combined during post-processing to enhance the final result.

Astrophotography cameras are typically monochromatic, meaning raw images are captured in black and white. To create a color image, filters are placed in front of the camera to isolate specific wavelengths of light.

Using multiple filters ensures that you capture the full spectrum of light emitted by your target, allowing for a more detailed and vibrant final image.

Post-processing consists of several steps, each critical to transforming raw data into a polished astrophotography image.

Astrophotography datasets often include dozens of individual FITS files per filter. The first step is aligning these images to correct any slight shifts between frames. Once aligned, the images are stacked to create a single “master frame” for each filter. This process, known as image integration, improves signal-to-noise ratio and removes artifacts like satellite trails or sensor imperfections.

After stacking, the master frames for each filter (e.g., Red, Green, Blue) are adjusted for contrast and brightness. This step ensures that the frames are balanced and ready for color combination.

The adjusted master frames are combined to create a final color image. By blending the data from the Red, Green, and Blue filters (and optionally Luminance or narrowband filters), you produce a detailed and true-to-life image.

In the final stage, you can tweak the contrast, brightness, and color balance of the image to highlight specific features or achieve your desired aesthetic. Advanced astrophotographers may use AI-based algorithms or specialized tools to further refine their images.

In astrophotography, the goal is to reveal what is already present in the data, not to create features that don’t exist. While creativity plays a significant role, it’s essential to stay true to the raw data and the celestial objects it represents. Different astrophotographers often produce vastly different results from the same dataset, showcasing their unique styles and expertise.

Post-processing relies on specialized software capable of handling FITS files and performing advanced image stacking, alignment, and editing. To learn more about the best software tools for astrophotography, from beginner-friendly options to professional-grade solutions, check out our article "What Software Do I Need for Astrophotography Post-Processing?".

Start your astrophotography journey today and unlock the full potential of your Telescope Live datasets!