State Library Victoria and other libraries have worked tirelessly to ensure some of the greatest historical literature on Astronomy is kept forever in digital form. Please explore these digital works!
Ptolemy Almagest - SLV's copy
Copernicus De revolutionibus orbium - Images from SLV’s copy (unfortunately, with Vatican censorship)
Kepler Astronomia nova - SLV copy too badly damaged to be used. Digitised version from Warnock Library via Rare Book Room
Newton Principa mathematica - SLV’s copy not digitised. Digitised copy from Stanford Library via Rare Book Room.