[color=#999999]This activity belongs to the [i]GeoGebra book[/i] [url=https://www.geogebra.org/m/sw2cat9w]GeoGebra Principia[/url].[/color][br][br][br]If we now add the apparent solar orbit, we'll have an [b]armillary sphere [/b][url=https://en.wikipedia.org/wiki/Armillary_sphere][img]https://www.geogebra.org/resource/scjbyz2p/0tuzuVw455vxurEw/material-scjbyz2p.png[/img][/url] (or spherical astrolabe) that enables us to analyze the passage of time (years, days, hours, GMT, UTC, seasons, zenith, obliquity of the ecliptic, vernal point, equinox, solstice, celestial coordinates, analemma, celestial horizon, sunrise, sunset, the 88 constellations, the zodiac, the brightest stars...) [[url=https://www.geogebra.org/m/sw2cat9w#material/er8nf4qt]20[/url]].

[color=#999999]Author of the construction of GeoGebra: [url=https://www.geogebra.org/u/rafael]Rafael Losada[/url]. The Right Ascension and Declination data for each star have been collected from: [url=https://www.geogebra.org/material/iframe/id/eehdnh2w]https://www.geogebra.org/material/iframe/id/eehdnh2w[/url] (see https://mathed.miamioh.edu/index.php/ggbj/article/view/189/157).[/color]