Credits & sources
ClutteredSky stands on decades of other people's careful work: star catalogues, sky surveys, spacecraft maps and orbital data. Here's where every piece comes from. The same list is in the app under Settings → Help & about → Credits & licences.
Data and imagery
HYG Database v4.1
Every star: position, brightness, colour and name. Also the star identities behind the constellation lines, and the stars in the app icon.
Changes: Filtered to stars of magnitude 9 and brighter (naked-eye stars, plus fainter ones for zoomed-in views and the few a constellation line ends on) and repacked into the app's own binary format.
OpenNGC
Every deep-sky object - the 110 Messier objects, the 109 Caldwell objects, and the brighter NGC and IC ones: positions, sizes, brightness, types and common names.
Changes: Reduced to the Messier and Caldwell lists plus the NGC/IC objects of magnitude 10 and brighter, and repacked into the app's own binary format. M102 is taken as NGC 5866 (a candidate OpenNGC itself notes), the Caldwell numbers are added from the published list, and short descriptions are generated from the type and constellation fields. Galaxy and globular-cluster magnitudes are taken from RC3 and Harris (below) where those cover the object.
Third Reference Catalogue of Bright Galaxies (RC3)
How bright each galaxy is: its total visual magnitude.
Changes: Total V computed as B_T - (B-V)_T.
Catalog of Parameters for Globular Clusters in the Milky Way
How bright each globular cluster is: its integrated visual magnitude.
Changes: Reduced to cluster name and V_t.
d3-celestial constellation lines
Which stars connect to which in the constellation figures, including the ones drawn in the app icon.
Changes: Each line's endpoints re-matched to HYG stars and stored by Hipparcos number rather than by coordinate.
The Milky Way panorama
The Milky Way glow.
Changes: Downsampled, converted to greyscale, individual stars filtered out and the dark-sky level subtracted.
Digitized Sky Survey (DSS2), colour
The object photographs shown when zoomed in on a Messier, Caldwell or bright NGC/IC object.
Changes: Cut out around each object with CDS's hips2fits service (from the CDS/P/DSS2/color HiPS), resized to 512x512 and the sky background subtracted.\n\nThe Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.\n\nThe Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation.\n\nThe UK Schmidt Telescope was operated by the Royal Observatory Edinburgh, with funding from the UK Science and Engineering Research Council (later the UK Particle Physics and Astronomy Research Council), until 1988 June, and thereafter by the Anglo-Australian Observatory.\n\nThis app made use of hips2fits, a service provided by CDS.
Solar System Scope planet textures
The surfaces of Mercury, Venus (its clouds), Mars, Saturn, Uranus and Neptune when zoomed in.
Changes: Desaturated by 15% (the pack's colours are deliberately a little richer than true), contrast-stretched, and reprojected from equirectangular maps to 512 px cube-map faces - and, fetched when zoomed in far enough, 1024 px ones from the 8k maps of Mercury, Mars and Saturn.
CGI Moon Kit: LROC colour map
The Moon's surface when zoomed in.
Changes: Contrast-stretched and reprojected to 1024 px cube-map faces, and to 2048 and 4096 px ones from the 16k map, cut into tiles and fetched when zoomed in far enough.
Cassini's Best Maps of Jupiter (PIA07782)
Jupiter's surface when zoomed in.
Changes: Contrast-stretched, reprojected to 512 px cube-map faces (1024 px fetched when zoomed in far enough), and turned so the Great Red Spot sits at its current longitude (it has drifted since the map was made in 2000).
USGS Astrogeology global mosaics
The surfaces of Io, Europa, Ganymede, Callisto, Pluto, Ceres and Vesta when zoomed in.
Changes: Downsampled, contrast-stretched, reprojected to 512 px cube-map faces (1024 px fetched when zoomed in far enough, all but Ceres), and - all of them being greyscale mosaics - each tinted one flat colour near the body's own (Io sulphur yellow, though its real colours vary more than that).
Meteor Shower Calendar working list
Each meteor shower's active dates, peak, hourly rate (ZHR), speed and parent body.
Changes: Transcribed for 13 major showers (via Wikipedia's list of meteor showers, which cites the IMO) and converted from dates to solar longitudes.
List of established meteor showers
Where each meteor shower's radiant is, and how far it drifts each day.
Changes: The median of each shower's published solutions (Jenniskens et al. 2020, Planetary and Space Science 182, 104821).
CelesTrak GP element sets
Where each satellite is: the orbital elements for the space stations and the brightest satellites, bundled as a snapshot; and which satellites those two groups contain.
Changes: Bundled exactly as served (CSV); propagated on the phone with SGP4.
Space-Track.org GP element sets
Where each satellite is, once the app has updated: the current orbital elements for the space stations, the brightest satellites and Starlink.
Changes: Fetched every two hours by the ClutteredSky server, in CelesTrak's column layout, and served as received; propagated on the phone with SGP4.
Quicksat intrinsic magnitudes
How bright each satellite is likely to look: its standard magnitude at 1000 km, scaled to the moment's range and phase.
Changes: Reduced to catalog number and magnitude; objects without a magnitude dropped.
adsb.lol aircraft positions
Where each aircraft is, how high and how fast, and its callsign, registration and type, while the Aircraft layer is on.
Changes: Fetched live for your area and drawn as received, moved along each aircraft's reported track between updates.
adsbdb flight routes
The scheduled origin and destination of a flight you select.
Changes: Looked up one flight at a time and kept on the phone for a day.
Wikidata airline designators
Which airline a flight belongs to: the operator name and radio callsign behind each three-letter ICAO airline code.
Changes: Current airlines only, one name per code, plus a handful of codes Wikidata lacks, added by hand.
Share-alike
The star and deep-sky catalogue bundled with the app, and the app icon drawn from it, are adaptations of HYG and OpenNGC. They are licensed under the same CC BY-SA 4.0 licence.
The maths
Positions come from published models: VSOP87 for the Sun and planets, Jean Meeus's Astronomical Algorithms for the Moon and much else, the IAU's rotation models for the planets' globes, and SGP4 for satellites. Each is checked against reference values in the project's tests.
Software
ClutteredSky is built with open-source libraries, including Android Jetpack and Kotlin. The full list, with each licence, is in the app under Settings → Help & about → Credits & licences → Software licences.