# Where do Astronomers usually get their wavelengths? Where do they turn to look up standard, accepted values for spectral features?

When identifying isolated observed spectral features or fitting complex observed spectra or even running complex numerical simulations, one needs a reliable, standard table of known wavelengths and other parameters like splitting, intensity relationships, etc.

Question: Where do Astronomers usually get their wavelengths? Are there a few favorite references where astronomers turn to look up standard, accepted values for spectral features?

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