Sky simulator, astronomical. Free and open source, Stellarium began in year 2000, is still updated and supported (on github since 2016) but builds have required at least Snow-Leopard/Intel since 2011. Here are the best versions that run on Leopard, Tiger, PowerPC, Panther, and Jaguar, and two relevant pdf manuals in this page's Manual Link.
Stellarium was hosted here until 2016, this no longer has the latest version but plenty of other information, downloads, and discussions.
Downloads 1, 2 & 3 are the highest Tiger versions 0.10.6
(**Note the 0.10.5 UB version is better/more-stable for Macs without CoreImage Videocards.)
Download 4 is the complete set of addon Star Catalogs and dozens of Location Backgrounds for Stellarium 10.5 and 10.6 (note these will likely NOT work for newer versions as the formatting has changed). Instructions for installation included.
Downloads 5 & 6 are the highest Leopard versions 0.11.3
Download 7 is the highest Panther PPC version 0.7.1
Download 8 is the highest Jaguar PPC version 0.5.2
