Sources & credits

Every map on this site is computed from real astronomical data. Here is where it comes from, who made it, and under which licence.

Hipparcos catalogue

The positions and brightness of the stars, measured by ESA’s Hipparcos satellite.

ESA – European Space Agency (1997) · ESA public data
XHIP – extended Hipparcos compilation

The compilation of Hipparcos data from which the stars on our maps are taken (VizieR catalogue V/137D).

F. Anderson & C. Francis (2012), Astronomy Letters 38 · Public astronomical data
d3-celestial

The ready-to-use file of 5,044 stars up to magnitude 6 (visible to the naked eye) and the lines of the 88 constellations.

Olaf Frohn · BSD 3-Clause
IAU constellations

The 88 official constellations, as defined by the International Astronomical Union.

International Astronomical Union (IAU) · Public reference
OpenStreetMap / Nominatim

The search for a place and its coordinates in the studio.

© OpenStreetMap contributors · ODbL 1.0
IANA Time Zone Database

The time zone and daylight saving time of the place and date you choose (through your browser).

IANA · Public domain
Astronomical Algorithms

The reference for the formulas used for precession and sidereal time.

Jean Meeus · Book (reference)
Fonts

Montserrat, Cormorant Garamond and Pinyon Script, served by us.

The Montserrat Project Authors · Christian Thalmann (Cormorant) · Rob Leuschke (Pinyon Script) · SIL Open Font License 1.1

How the sky is computed

For the place, date and local time you choose, we convert the time to universal time, compute the local sidereal time, correct the star positions for the precession of the equinoxes since the year 2000, then project the visible half of the sky onto a disc (stereographic projection, north up, east on the left as when looking up). Accuracy is about a tenth of a degree, far finer than a poster can show.

The map is an artistic rendering of real data: stars fainter than magnitude 6, planets and the Moon are not drawn.

d3-celestial licence notice

Copyright (c) 2015, Olaf Frohn
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.