Moon & Star Map

The real moon phase on any date and the night sky over any city, as printable keepsakes.

Moon & Star Map answers "what was the moon on my birthday?" with the exact phase, illumination and moon age computed from astronomical algorithms (Jean Meeus), checks whether two moons "complete each other", shows a moon-phase calendar for any month, and draws the sky above a city at a chosen date and time: about 2,900 stars from the Yale Bright Star Catalog, constellation lines, the horizon, the cardinal points and the Moon in its real position. Posters download as vector PDF (12x18 in, 18x24 in, A3, Letter, A4, with 0.125 in bleed) and SVG.

What it does

Moon phase for one or many dates: phase name, illumination %, moon age, waxing or waning, exact new/quarter/full moon times, next full and new moon
Two dates: do the two moons complete each other (half a lunar cycle apart)? Match score and an honest explanation
Moon-phase calendar for any month, with exact phase times in the city's time zone
Star map of the real sky above a city at a date and local time, time zones and daylight saving time handled
Vector poster PDFs at 12x18 in, 18x24 in, A3, Letter and A4 with bleed, plus SVG and a shareable view page
Moon posters: a single date, a pair of dates, or a full-year lunar calendar
Data: GeoNames cities (CC BY 4.0), Yale Bright Star Catalog, constellation lines from d3-celestial by Olaf Frohn (BSD-3-Clause), astronomia (MIT)

Try asking ChatGPT

“What was the moon phase on 1998-07-14?”

“Do our moons complete each other? Anna 1996-05-02, Ben 1997-11-20”

“Star map over Austin, Texas on 2019-06-21 at 22:15 titled 'The night we met'”

Limitations

Decorative keepsakes: positions are accurate to a fraction of a degree, but this is not for navigation or scientific use
Planets, the Milky Way and atmospheric effects are not drawn; stars brighter than magnitude 5.5 are shown
Supported years 1800-2200; cities are matched from a list of about 11,000 places (all US, Canada, UK, Ireland, Australia and New Zealand towns of 15,000+ and the largest cities worldwide)
PDF text supports Latin, Greek and Cyrillic letters; Chinese, Japanese and Korean titles appear only in the SVG

Connect

Install Moon & Star Map from the ChatGPT plugin directory. Developers can connect the MCP endpoint directly: https://sky-keepsake.zovo.one/mcp