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NASA’s Astronomy Picture of the Day for September 27, 2026, compares a long-exposure image of the Andromeda galaxy before and after software processing. The 223-image stack contains airplane and satellite trails, cosmic-ray streaks and bad pixels; several astronomy programs reduced those artifacts to make the galaxy clearer.
NASA’s Astronomy Picture of the Day on September 27, 2026, showed a raw and a processed image of the Andromeda galaxy, illustrating how software can reduce trails and camera defects in an astronomical photograph. The original image combines 223 exposures taken in Portugal in 2019; processing was used to limit features caused by activity near Earth and by the camera, rather than by the distant galaxy.
Each of the 223 images in the stack was a 300-second exposure, according to NASA’s explanation. The photographs were taken from a garden observatory in Portugal. In the unprocessed view, the combined data show parallel airplane trails, continuous satellite trails, short streaks from cosmic rays and defective pixels.
NASA says the artifacts were greatly reduced using several software packages: Astro Pixel Processor, DeepSkyStacker and PixInsight. Despite the title’s reference to Photoshop, the explanation says Photoshop was not specifically used for the work.
The image credit goes to Kees Scherer. NASA’s APOD editors describe the processing as an effort to reduce features unrelated to M31, so the galaxy is easier to see. The comparison does not provide technical settings or a detailed account of each processing step.
Separating Galaxy From Image Artifacts
The comparison shows how astronomical images can record light from a target alongside effects from the observing environment and imaging equipment. In this case, aircraft and satellites left trails across the sky, while cosmic rays and bad pixels produced other marks in the data.
The before-and-after images show the result of reducing those artifacts. NASA says the processing was intended to represent Andromeda more clearly. The source does not quantify the changes made to the image or compare the result with other processing methods.
A 2019 Stack From Portugal
Andromeda, also known as M31, is described by NASA as the Milky Way’s closest major galactic neighbor. The APOD entry explains that its featured comparison comes from observations made in 2019, not from a new observation announced on September 27, 2026. The date marks the publication of the image and explanation.
APOD is NASA’s daily feature of an image or photograph of the cosmos with an explanation written by a professional astronomer. The September 27 entry was authored and edited by Robert Nemiroff, Jerry Bonnell, Cecilia Chirenti and Keighley Rockcliffe, and credited as a service of NASA’s Goddard Space Flight Center, NASA Science Activation and Michigan Technological University.
Processing Details Not Supplied
NASA’s explanation does not specify which software package handled each correction, what settings were applied, or how much any individual artifact was reduced. It also does not provide an independent comparison of the processed image with other treatments of the same exposures. The entry presents the processing goal, but readers cannot use the supplied description alone to reproduce the workflow.
The source describes the artifacts visible in the before image and says they were greatly reduced; it does not claim that every artifact was removed. It offers no further technical assessment of what processing may have changed in the final image.
APOD Continues With Daily Images
The September 27 entry points readers to the APOD submissions page, noting that the email address for image submissions has changed. NASA also says APOD’s main site is moving from apod.nasa.gov to science.nasa.gov/apod. The source does not give a completion date for that move.
The entry lists “cosmic latte” as the subject of the next day’s picture. No additional announcement or follow-up about the Andromeda processing is included.
Key Questions
Was Photoshop used to process the Andromeda image?
NASA’s explanation says Photoshop was not specifically used. It names Astro Pixel Processor, DeepSkyStacker and PixInsight as part of the processing workflow.
How many exposures make up the image?
The stack contains 223 images, each with an exposure time of 300 seconds.
What caused the streaks and defects in the raw view?
NASA identifies airplane trails, satellite trails, cosmic-ray streaks and bad pixels. These are artifacts of the observing environment or camera, rather than features of Andromeda.
When and where were the photographs taken?
The images were taken in 2019 from a garden observatory in Portugal. NASA published the comparison as APOD on September 27, 2026.
Source: primary
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