Free Star Map Generator
Most “free star map” sites are storefronts where free means a thumbnail. Here is the actual deal, stated up front.
Open the free generator
Free, in your browser — no account, nothing uploaded. Free downloads carry a small watermark; a clean high-resolution print export is planned as a paid upgrade.
What is genuinely free
- Unlimited maps — every date, place, theme, size and caption option, no cap.
- Downloads — an SVG and a screen-resolution PNG of any map you make, each carrying a small watermark.
- No account, no email, no upload — the page is static and the astronomy runs in your browser; your data never leaves it. It even works offline once loaded.
What is not free
One thing: the clean, high-resolution print file (~300 dpi PNG/PDF, no watermark) is a paid export. Full honesty: the checkout for it isn't even live yet — the button in the generator says so rather than pretending.
That's the whole model. No subscription, no locked features dressed up as a trial, no watermark on the on-screen experience — just a small mark on the free files that the paid poster file removes.
How the map is computed
Your date, time and place are converted to a Julian Date and then to local sidereal time — the astronomer’s clock for “which way is the sky facing.” Each of the 1,630 stars in the Yale Bright Star Catalogue (every star brighter than magnitude 5.0, i.e. everything a good naked eye can see) is transformed to its altitude and azimuth at that exact moment, and everything above the horizon is projected onto the circular chart: zenith at the centre, horizon at the rim, north at the top — and east on the left, because a star map is read looking up, which mirrors east and west compared to a ground map.
The 89 constellation figures are drawn with the same math and clipped at the horizon. Star dots are scaled by real brightness (magnitude) and tinted by star colour. Everything runs in your browser — nothing is uploaded, there is no account, and the page works offline once loaded.
Common questions
Is it really free?
The generator, all its options, and the watermarked SVG/PNG downloads are free without an account. Only the high-resolution unwatermarked print file is paid (and it isn't purchasable yet — in the meantime, everything else works).
Why is there a watermark on the free downloads?
It's the line between the free tool and the print product that is meant to fund it. The watermark is a faint diagonal mark plus a small credit line — the map itself is complete and accurate.
Do you collect my data?
No. There is no backend: no accounts, no analytics calls, no server that ever sees your dates and places. You can verify this — the page is a static file and the source is readable.