KeptStars research · shared-sky
Calculated 2026-11-09.

Install numpy and skyfield==1.54. Download original HYG v4.1 and JPL de421.bsp from the sources in method.json. Run python build.py --catalog hygdata_v41.csv --ephemeris de421.bsp. Source catalogue SHA256 is in method.json. This pack includes the selected subset for audit, not the full upstream catalogue.

DATA LICENCE: CC BY-SA 4.0
https://creativecommons.org/licenses/by-sa/4.0/
KeptStars Team; HYG v4.1 / David Nash, Astronexus. Identify changes and retain CC BY-SA 4.0.

Public study: https://keptstars.com/blog/shared-sky-different-cities
Method and limitations: method.json
