Moon landing · Houston
20 July 1969 at 21:56 local time. Changing place rotates the horizon and changes which stars are visible.
Create a Sky Map for Any Date and Place
Recreate the visible sky with real catalogue stars for a date, local time and location—free, with no sign-up. Customize constellations, planets, labels and layout, then download a high-resolution file generated in your browser.
Build your map
Astronomical mode plots catalogue stars above your local horizon. Location coordinates never leave this page.
Daylight-saving time is not inferred; choose the offset that applied.
Decorative mode: this seeded starfield does not represent the sky on any date or at any location. Its compass and grid are artistic guides only.
The seed stays fixed while you style the design.
Map summary will appear after generation.
Accuracy note: suitable for artwork and learning, not navigation or telescope alignment. Very faint stars, deep-sky objects, atmospheric refraction and terrain are not shown.
Style and sky layers
Higher values include fainter catalogue stars.
Theme
Export
2400 × 2400 px · 8 × 8 in at 300 DPI
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One-click styles
Worked sky-map examples
Millennium · Sydney
1 January 2000 at midnight. Turn constellations on to recognize the southern sky.
Seeded wallpaper · luna-42
Random mode uses FNV-1a and Mulberry32. The same seed and settings reproduce the exact visible pattern.
How to create and use a sky map
- Choose Real sky, a suggested city, date, local time and UTC offset.
- Generate the map, then toggle constellations, labels, planets, grid and theme; styling updates do not change the chosen sky.
- Add poster text, select exact pixel dimensions and download PNG or PDF.
- Copy the share link to recreate every setting, or switch to Random starfield for non-astronomical artwork.
What the controls change
The magnitude limit controls how faint a catalogue star may be; a higher number shows more faint stars. Rotation changes page orientation only. The real-sky grid shows altitude circles and azimuth spokes. Circles, spokes and compass labels in random mode are decorative.
Export guidance and permitted uses
Pixel dimensions—not labels like “poster-ready”—determine printable size. At 300 DPI, 2400 × 3000 pixels prints at 8 × 10 inches; 1600 pixels is about 5.3 inches. Generated files have no watermark and may be used in personal or commercial posters, gifts, classroom materials, tattoos, wallpapers and designs.
Accuracy and methodology
- Star catalogue
- 93-star page-local bright-star extract based on HYG/Hipparcos and Yale Bright Star data; J2000 equatorial coordinates, magnitude limit +3.0.
- Astronomy engine
- Astronomy Engine 2.1.8 for apparent topocentric Sun, Moon and planet positions, with a local sidereal fallback if unavailable.
- Coordinates & projection
- J2000 RA/declination precessed to date and converted to altitude/azimuth. Circular maps use azimuthal equidistant projection; rectangular maps use an altitude–azimuth plot.
- Timezone & range
- Explicit numeric UTC offset; 1900–2100. Select historical daylight-saving offsets manually.
- Expected precision
- Typically within about 1° for bright stars; stellar proper motion, atmospheric refraction, terrain and deep-sky objects are omitted. Not for navigation.
- Privacy & rights
- Coordinates, rendering and files stay local. Geolocation is requested only on click. Free, no watermark; commercial use permitted.
- Random mode
- FNV-1a seed hash, Mulberry32 PRNG, uniform hemisphere sampling and decorative orthographic projection; no scientific meaning.
- Last reviewed
- 17 July 2026.
Technical equations and pseudocode
Uniform sphere: z = 2u − 1; φ = 2πv; x = √(1−z²)cosφ; y = √(1−z²)sinφ. Random mode samples until the requested number is visible, rather than counting a hidden hemisphere.
Horizon conversion: H = LST − RA; sin(alt) = sin(lat)sin(dec) + cos(lat)cos(dec)cos(H). Azimuth comes from the corresponding two-argument atan2 expression; radius is (90° − altitude) / 90°.
Brightness: catalogue radius is proportional to 10^(−0.2 × magnitude). Random brightness uses b = 0.35 + 0.65 × random^1.6.
Seed: UTF-16 code units are folded with 32-bit FNV-1a, then Mulberry32 produces each deterministic sample.
Sky map generator FAQ
Is this the real sky or a random design?
Real sky mode plots catalogue stars above the horizon for the entered date, time and coordinates. Random starfield mode is decorative and is clearly labelled as such.
How accurate is the sky map?
Bright-star positions use J2000 catalogue coordinates precessed to the selected date, local sidereal time and a horizon projection. Planet positions use Astronomy Engine when available. It is suitable for education and artwork, not navigation or telescope pointing.
Can I choose a historical or future date?
Yes. The supported range is 1900 through 2100; accuracy is best near the present because stellar proper motion is not modelled.
How are timezones handled?
The selected numeric UTC offset converts the entered local clock time to UTC. Daylight-saving changes are not inferred, so choose the offset that applied on the selected date.
Is it free and is there a watermark?
Yes. The generator is free, requires no sign-up and adds no watermark.
Can I print or commercially use the image?
Yes. You may use generated files for personal or commercial projects. Star names and astronomical facts are not copyrightable, but you remain responsible for other text you add.
What resolution should I choose?
At 300 DPI, divide pixels by 300 to estimate print inches. A4 uses 2480 by 3508 pixels; 8 by 10 inches uses 2400 by 3000 pixels.
Can I share or recreate a map?
Yes. Copy share link stores the relevant settings in the URL. Random maps can also be recreated from their seed.
Are locations uploaded?
No. City presets, coordinates, rendering and export stay in your browser. Browser location is requested only after you press Use my location.
What is the difference between a sky map, star chart and starfield?
Sky map and star chart usually mean a positional diagram of real celestial objects. A starfield may simply be a decorative pattern; this page provides both in separate modes.