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Real-sky image fixtures: provenance and licences

Collected on 2026-08-30. These fixtures are authentic camera/astronomical images, not AI-generated or synthetic star fields. The three image files are exact byte copies of their upstream originals; only the local filenames were changed. No resizing, cropping, tone mapping, or transcoding was performed.

The images total 7,936,991 bytes (about 7.57 MiB), comfortably below the 30 MiB fixture budget.

Inventory

Local file Test role Format and dimensions Bytes SHA-256
esa_tetra3_alt40_az-135_20190729.tiff Wide-field, low-SNR, raw 16-bit camera frame TIFF, 1024 x 768, 16-bit grayscale 1,573,184 f5d6c27ac7e8e2114fbeb45196380703e138031819714db7e39f3e101b32b557
esa_tetra3_alt60_az-135_20190729.tiff Wide-field, low-SNR, raw 16-bit camera frame TIFF, 1024 x 768, 16-bit grayscale 1,573,184 f288f6e1fb3a1299626956e3d44740c0260348c65dd9296ac8e07bb27524a5e9
wikimedia_m31_cc0_20190830.png Narrower deep-sky target with dense stellar background and companion galaxies PNG, 4144 x 2822, RGBA 4,790,623 9edbcaab9576e9ee9e7226c97118617c2d74e793b3281d5e56eac68319a05494

ESA tetra3 real-world camera frames

Applies to:

  • esa_tetra3_alt40_az-135_20190729.tiff
  • esa_tetra3_alt60_az-135_20190729.tiff

Source and authenticity

Licence

  • Repository-level licence: Apache License 2.0. No per-image exception is present in the source tree.
  • A verbatim copy is included as LICENSE-ESA-TETRA3-APACHE-2.0.txt (SHA-256 d6cbf26a85a5855d30156b89e24adfaaad6a4cd5c6944b08850c1e36f92352dd).
  • The image bytes were not modified.

Plate-solve verification values

These values are derived verification aids, not embedded EXIF. Each original image was blind-solved with tetra3's bundled default database and distortion=[-0.2, 0.1]. The solver reports J2000 equinox coordinates; horizontal FOV and residuals are in degrees and arcseconds respectively.

Local file Centre RA Centre Dec Horizontal FOV Roll Matches RMS residual
esa_tetra3_alt40_az-135_20190729.tiff 230.667360 deg +11.034223 deg 11.426214 deg 332.279807 deg 11 6.461 arcsec
esa_tetra3_alt60_az-135_20190729.tiff 240.464077 deg +28.940573 deg 11.421557 deg 329.049101 deg 16 5.024 arcsec

The TIFF tags contain image geometry, 16-bit sample depth, uncompressed storage, and a tifffile.py software tag. They do not contain camera make/model, focal length, GPS, an absolute timezone, or celestial WCS.

Wikimedia Commons M31 photograph

Applies to wikimedia_m31_cc0_20190830.png.

Source and authenticity

  • Author: Stephen Rahn (StephenGA / srahn on Flickr), Macon, Georgia, USA.
  • Capture/publication date stated by the source: 2019-08-30 00:17; timezone unspecified.
  • Stable Wikimedia Commons description page: File:Messier 31 (48645809527).png.
  • Upstream original: Messier_31_(48645809527).png.
  • The Commons page records that the image came from the author's Flickr photograph 48645809527 and that Wikimedia's FlickreviewR 2 verified its licence on 2020-11-11.

Licence

Known sky content

  • Primary object: M31 / NGC 224, the Andromeda Galaxy. Its compact companion M32 and diffuse companion M110 are also visible in the frame.
  • Reference position from CDS SIMBAD: ICRS J2000 RA 00h 42m 44.330s, Dec +41d 16m 07.50s (decimal RA 10.6847083 deg, Dec +41.2687500 deg). SIMBAD gives an optical angular size of about 199.53 x 70.79 arcmin, position angle 35 deg.
  • This is the narrower/deep-sky fixture relative to the 11.4-degree ESA frames. The PNG contains no EXIF or WCS, so the M31 coordinate is a catalogue reference for the depicted target, not a claim that the exact image centre or plate scale is embedded in the file.

Integrity/metadata check

The format, dimensions, bit depth/mode, byte lengths, and hashes above were read after download with Pillow and SHA-256. All files opened successfully as single-frame images. Hashes should be checked before using a fixture as a golden test input.