Skyfold Star Map Poster

What it is for

This tool draws the sky exactly as it stood above a place at a local date and time — stars, constellation figures, the Moon and the planets — and turns it into a print-ready poster. People use it for gifts that mark a birth, a wedding or a first date, for classroom handouts, or simply to keep a record of a memorable night.

You get an SVG and a one-page PDF at the chosen paper size, both vector, so they stay sharp at any print size. It is the same drawing as the Star-map poster tab of the Skyfold app, where you also get a live preview and a 300 dpi PNG export. The map shows the geometric sky: no clouds, no light pollution and no Milky Way band.

Worked example

The first example uses Paris (48.8566, 2.3522, time zone Europe/Paris) on 14 June 2019 at 23:30, style Ivory print, paper A3 portrait (297 × 420 mm), faintest stars magnitude 6, title The night we met and place line Paris, France.

The summary reports 2321 stars, 82 constellation lines and 5 Moon and planets above the horizon. The table of the brightest stars starts with Arcturus in Boötes (magnitude −0.05, altitude 58.3° in the south-south-west, 37 light years away), followed by Vega (0.03, 52.2° in the east) and Capella low in the north at 8.9°. The planet table puts the Moon at azimuth 175.1° and altitude 25.7° — due south — with Jupiter at 13.9° in the south-south-east, while Mercury, Mars and Saturn all hug the horizon below 2°.

The two download blocks give you the SVG and the PDF. The second example, Tokyo on New Year 2027 in Black and gold on a square sheet with star names, shows 1420 stars at magnitude 5.5.

How to read the result

• The preview is a zenithal chart: the centre is the point overhead and the circle is the horizon. North is up and east is on the left, because you look up at the sky.
• Brightest stars above the horizon lists the leading stars with constellation, magnitude, position and distance — handy for a caption or a back-of-card note.
• Moon and planets on the map lists what is drawn besides the stars.
• The warnings tell you when the Sun is less than 6° below the horizon (the real sky would be too bright) and when characters in your texts cannot be written in the PDF's standard fonts.

Tips and common mistakes

• Check the time zone: a poster for 23:30 in Paris must use Europe/Paris, otherwise the sky turns by hours.
• Magnitude 6 resembles a dark country sky; choose 4.5 to 5 for a cleaner, less busy design.
• For Japanese, Arabic or other non-Latin titles, use the SVG: the PDF replaces characters outside Western European text and says so.
• Leave the date line empty to print the local date and time automatically.
• Print shops prefer the PDF; designers prefer the SVG for further layout.

FAQ

Is this the real sky or an artistic approximation?

It is the computed sky: 8 920 catalogued stars from the HYG database are precessed to the date and placed with the observer's local sidereal time; the Moon and planets come from the same ephemeris as Skyfold's position tool.

Can I use the poster commercially?

Your poster is yours. The star data is derived from HYG v4.1 under CC BY-SA 4.0 and the constellation figures from d3-celestial (BSD licence); credit both if you publish the map.

Why is east on the left?

A sky chart is a view upwards. Hold it above your head with the top pointing north and it matches the sky.

Which paper sizes are available?

A4, A3 and A2 portrait, US Letter, 12 × 16 in, 18 × 24 in and a 300 × 300 mm square.