Epic: Star Catalogues & Deep Sky Data

[zworkb]

Problem

Current skydata only contains stars up to magnitude ~7 (Norder 0+1 from Stellarium build). Deeper tiles cannot be downloaded from stellarium-web.org (server returns HTML). EPH tiles must be generated from raw catalogues.

Sub-issues

• Reverse-engineer Stellarium EPH tile binary format #73 Reverse-engineer Stellarium EPH tile binary format
• Download Gaia DR3 subset (mag ≤ 12) for tile generation #74 Download Gaia DR3 subset (mag ≤ 12)
• Build EPH tile generator from star catalogues #75 Build EPH tile generator from star catalogues
• Generate DSO tiles from NGC/IC catalogues #76 Generate DSO tiles from NGC/IC catalogues
• Update comet and minor planet data from MPC #77 Update comet and minor planet data from MPC
• Update Makefile and download scripts for generated tiles #78 Update Makefile and download scripts for generated tiles

Data Sources

• Gaia DR3 — 1.8 billion sources
• Hipparcos — 118,218 bright stars
• OpenNGC — deep sky objects
• MPC — comets and minor planets

Notes

• EPH = Stellarium's proprietary binary HEALPix tile format
• Tile structure: skydata/stars/NorderN/Dir0/NpixM.eph
• Engine's stars_limit_mag is FOV-dependent — fainter stars only shown at higher zoom
• Norder 0 = 12 tiles, Norder 3 = 768 tiles, Norder 6 = 49152 tiles