The Astronomy Picture of the Day (APOD) this week showcases the Andromeda galaxy (M31) in a before‑and‑after comparison. The “before” image is a stack of 223 separate exposures, each 300 seconds long, taken from a garden observatory in Portugal during 2019. The long exposure reveals the galaxy through Earth’s busy skies, but also shows the typical imperfections of a digital camera: bright parallel airplane trails, long continuous satellite trails, short cosmic‑ray streaks and bad pixels.
In the “after” image, those Earthly artefacts were not removed with Photoshop but were largely reduced using a suite of astronomical software, including Astro Pixel Processor, DeepSkyStacker and PixInsight. The processing was carried out to minimise terrestrial interference and to present a clearer view of Andromeda, rather than to create a digital fantasy.
Andromeda is the Milky Way’s nearest major galactic neighbour, and the APOD explanation stresses that the image aims to show what the galaxy really looks like from our perspective, free from the visual noise introduced by the atmosphere and the camera.
Credits for the image go to Kees Scherer. The APOD team for this release includes Robert Nemiroff, Jerry Bonnell, Cecilia Chirenti and Keighley Rockcliffe, and the service is provided by the Astrophysics Science Division at NASA’s Goddard Space Flight Center, NASA Science Activation and Michigan Technological University.
APOD has updated its image‑submission email address and is moving its main site from apod.nasa.gov to science.nasa.gov/apod. The next picture in the series will be titled “cosmic latte.”
<small>Source: NASA — read the original story there.</small>
