The twelve sessions
Each download is one zip of about half a gigabyte (6.0 GB for all twelve). Each is stored on Zenodo, which gives it a permanent address (a DOI) and keeps it available, separately from this website. The pictures are what OriginStack 2.21 produced from that session with the default settings.
Whirlpool Galaxy (M51)
Face-on spiral galaxy · 45 × 20 s, 15 minutes · captured 2026-07-01 · picture cropped to the galaxies
The standard test: a face-on galaxy in a wide, star-filled field.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 2.7 px. The picture above is what that run produced.
SHA-256 of the zip: f6e46e6dc5c8543e5bbeadbd8fa1d7d33ef4914c1de59d5394b33faef0c3e9b8
python originstack.py -d "01_face-on_spiral_galaxy_M51_Whirlpool" -o stack.fits
Sculptor Galaxy (NGC 253)
Large galaxy · 45 × 10 s, 8 minutes · captured 2025-10-11
A galaxy that fills much of the frame, so there is little empty sky for the background fit.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 3.6 px. The picture above is what that run produced.
SHA-256 of the zip: 1d2a669aee61e17f0260c9351cf7f23a1b6f1163146a45390144c8174dc1306c
python originstack.py -d "02_large_galaxy_NGC253_Sculptor" -o stack.fits
Stephan's Quintet
Galaxy group · 45 × 10 s, 8 minutes · captured 2025-10-11
A compact galaxy group: faint fuzzy patches among many stars.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 3.9 px. The picture above is what that run produced.
SHA-256 of the zip: 9b23bbf118459a9aaa96bfdc15237d328de9959f89be5420b7f36e6c20006559
python originstack.py -d "03_galaxy_group_Stephans_Quintet" -o stack.fits
Flame Nebula (NGC 2024)
Emission nebula · 45 × 10 s, 8 minutes · captured 2025-12-10
Faint nebulosity beside a very bright star, which tests the background and star handling.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 3.9 px. The picture above is what that run produced.
SHA-256 of the zip: 4d089b055892b685444874dded71ef8e4808c0708cdeb0b8565ed5685b7d0cee
python originstack.py -d "04_emission_nebula_Flame" -o stack.fits
Iris Nebula (NGC 7023)
Reflection nebula · 45 × 10 s, 8 minutes · captured 2025-10-08
Blue reflection nebulosity around a bright star.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 5.0 px. The picture above is what that run produced.
SHA-256 of the zip: fd8d871c59b0f84767734a2a557a735de2226c58101354b0b27648345a67f863
python originstack.py -d "05_reflection_nebula_NGC7023_Iris" -o stack.fits
Eastern Veil Nebula (NGC 6995)
Supernova remnant · 45 × 10 s, 8 minutes · captured 2026-09-29
Delicate filaments that depend on a clean background.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 3.2 px. The picture above is what that run produced.
SHA-256 of the zip: df3e49ba539343582918427c118158e8ab1dd874ca940bc72389b920303a66b8
python originstack.py -d "06_supernova_remnant_Eastern_Veil_NGC6995" -o stack.fits
Dumbbell Nebula (M27)
Planetary nebula · 42 × 10 s, 7 minutes · captured 2026-09-01
A bright, compact nebula in a rich star field.
Checksum and command
42 frames; with OriginStack 2.21 40 of 42 are accepted, median star width about 5.0 px. The picture above is what that run produced.
SHA-256 of the zip: a3f27bae1342864317fda3566808670ff9d51c923821fcb7e1e9d07be46aea8a
python originstack.py -d "07_planetary_nebula_M27_Dumbbell" -o stack.fits
Great Hercules Cluster (M13)
Globular cluster · 45 × 15 s, 11 minutes · captured 2026-09-29
A dense stellar core: star detection and registration on a crowded field.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 5.0 px. The picture above is what that run produced.
SHA-256 of the zip: 38b9ac9b1e4750858a55ad93af1f9cee8f91e6d7d06ce26ad4fb1aef5e0fcc5b
python originstack.py -d "08_globular_cluster_M13_Hercules" -o stack.fits
Messier 37
Open cluster · 45 × 30 s, 22 minutes · captured 2025-12-11
Hundreds of stars per frame, with no nebulosity to guide the background fit.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 6.8 px. The picture above is what that run produced.
SHA-256 of the zip: 8a026e040ea72c9a716053a62bd66aa924c4b21f7c6bc6e685d6115d17783260
python originstack.py -d "09_open_cluster_M37" -o stack.fits
Sagittarius Star Cloud (M24)
Wide-field Milky Way · 45 × 5 s, 4 minutes · captured 2025-09-15 · picture cropped to the middle of the field
A wide star field: lots of stars, almost no empty sky.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 7.5 px. The picture above is what that run produced.
SHA-256 of the zip: 8ca7ec9a46eb21dfaf7596ccb2a14a463922de1aa6056c7dfa57853ad2dad3ca
python originstack.py -d "10_wide_field_Sagittarius_Star_Cloud" -o stack.fits
Comet C/2025 R2 (SWAN)
Comet · 45 × 10 s, 8 minutes · captured 2025-10-20
A comet moving against the stars: stack it twice, once on the stars and once on the comet.
Stack it with comet mode: choose the Comet card in the app, or add --comet-mode on the command line.
Checksum and command
45 frames; with OriginStack 2.21 45 of 45 are accepted, median star width about 6.2 px. The picture above is what that run produced.
SHA-256 of the zip: 15d6a90a8ba62915995a6534627aa16eec5012a15f943104d1df95ac3750ee81
python originstack.py -d "11_comet_C2025_R2_SWAN" -o stack.fits --comet-mode
Lagoon Nebula (M8), OIII session
Narrowband emission nebula · 45 × 25 s, 19 minutes · captured 2026-08-25
A narrowband session through an OIII filter: a very different colour balance, and wider stars.
Checksum and command
45 frames; with OriginStack 2.21 42 of 45 are accepted, median star width about 10.7 px. The picture above is what that run produced.
SHA-256 of the zip: a02ad758ace4aea43ee4791cda05a2e999d2d3e0747a4048f03f0cc041c079e5
python originstack.py -d "12_narrowband_OIII_Lagoon" -o stack.fits
Using one
- 1. Download and unzip
Download a zip, unzip it, and you get one folder with the light frames (
Light0001.fitsand so on), the session’s owndark,flatandbiasframes andinfo.json. Keep everything in that folder.- 2. Choose the folder in OriginStack
In the desktop app, choose the folder as the light-frames folder and press Start. The app reads the target from the session and picks sensible settings. From a terminal it is
python originstack.py -d FOLDER -o stack.fits. The first time you do this, the sample session page walks through every step.- 3. Compare with the picture on this page
The result should look very like the one above, though newer versions may differ a little. Each card lists how many frames were accepted and the typical star width, so you can check your numbers against ours.
- The comet and the narrowband session
The comet needs comet mode (the Comet card in the app, or
--comet-mode) to stack on the comet as well as on the stars. The Lagoon Nebula session was shot through an OIII filter (the FITS headers call it “Nebula”), so its colours and star sizes differ from the broadband sessions.
Why these twelve
Different targets stress different parts of the stacker: a galaxy that fills the frame leaves little sky to fit the background to, a cluster leaves no nebulosity to guide it, and a comet moves. Each session was picked from a large archive for sharp, steady frames, with nothing rejected by the Origin and the target clearly visible in the Origin’s own stack. From each, the best frame of every stretch of the night was kept, so the sets cover the whole session instead of its best five minutes.
- What was removed
The observer’s location (latitude, longitude, altitude, GPS and airmass), the capture app’s session id and the camera’s serial number were removed from the FITS headers and the json files. The pixel data is untouched. The capture date and time and the target’s coordinates stay, since they say when and where in the sky the telescope pointed.
- Not a full night
42 to 45 frames is a short session, so a stack is noisier than one of a few hundred frames. It is enough to show every step working. The gallery shows what longer sessions give.
Licence and credit
The data is released under the Creative Commons Attribution 4.0 licence: use it for anything, including teaching, testing other software and sharing your results, as long as you credit “OriginStack” and link to the Zenodo record you used. The records are listed on Zenodo under the name OriginStack; the software itself is free under the GNU GPL v3.
Questions or problems?
A download that will not unzip, a session that will not stack, or a question about using the data? Open an issue on GitHub (the quickest way to get an answer, and others can find it later), or write to originstack@originstack.site.