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WorldWide Telescope vs Celestia: catalog facts
WorldWide Telescope	Celestia
Free Free and open source.	Free Free and open source.
Web	Windows, macOS, Linux
Large collection of sky imagery in the browser Guided tours with narration and slides	Free, real-time 3D exploration of space Move freely between planets, stars and galaxies
Needs a fast internet connection Interface can feel dense for newcomers	Project website blocks automated visitors with a proof-of-work check A simulator for exploration rather than a structured astronomy course
Web application	Downloadable app
Open source	Open source
License not stated	License: GPL-2.0
Not stated if an account is needed	No account needed
Needs internet	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.