The original download page on SpaceEngine.org is often down, but you can access it via the Wayback Machine to find direct links. Direct Community Mirrors:
The full installer is roughly 1 GB , with an additional 100 MB patch for version 0.9.8.0e . Key Features of 0.9.8.0 space engine 0980 download repack full
, it has since been discontinued on the official website. Below is a blog-style overview of how to find and install this legacy version, along with the precautions you should take. The original download page on SpaceEngine