Bookshelf Planetarium

The Texas sky right now, with the constellations renamed after the bookshelf.

How it works: local sidereal time from the clock and your longitude, each star's right ascension and declination turned into altitude and azimuth, then a stereographic projection with the zenith in the middle and the horizon at the rim (hold it overhead: north at the top, east on the left). The Sun, Moon and planets use low-precision orbital elements (Meeus, Schlyter) and the catalogue is J2000, so positions are good to a degree or two, which is about the width of your thumb at arm's length. Twilight on the rim follows the Sun's altitude.

Each day the 88 constellations are dealt out to authors from the library, weighted so the authors with the most books get the most sky. Stars to magnitude 5 and constellation lines from d3-celestial by Olaf Frohn (BSD-3-Clause), reduced; no data leaves your browser.

Bookshelf Planetarium

This is the real sky over Texas (or wherever you tell it) at the time on the clock. The dome view is an all-sky chart meant to be held above your head; "look around" is the view from the ground, drag to turn. The constellations keep their shapes but each one is renamed, for today only, after an author from Jack's bookshelf: the authors with the most books get the biggest constellations, and the deal is reshuffled every midnight. Click a constellation for its real name, the author's books and the myth the sky made up for them.

← →ten minutes back / forward (shift: one hour) spaceplay / pause Nreturn to now Ttonight at 23:00 Vdome / look around Lcycle labels escdeselect

Star positions, magnitudes and B−V colours, star names and constellation lines come from d3-celestial by Olaf Frohn (BSD-3-Clause), cut to stars brighter than magnitude 5. Sun, Moon and planets use low-precision formulas accurate to a degree or two. The skyline and its water tower are invented.