Audio description is a very good idea, but it could be enhanced by adding the possibility to have subtitles too.
Subtitiles could be read from a normal .txt file like the audio descriptions that are simply .mp3 file.
Adding this option could be useful for developing future multilingual versions of Starry Night. Users could translate descriptions and record their own voice for audio descriptions. Also these descriptions you could make available as data updates, as you already do for celestial objects.Users may also add audio descriptions for currently unprovided objects.
Also, I think that adding subtitles to the audio descriptions could be an useful idea. It could be better to have the possibility to have translations into several languages.