Linked from
The 9 pages that link to Spectroscope, each with the reason it gives.
Flame testRelated: A spectroscope reveals spectral lines that a color-only test cannot resolve.
Fraunhofer linesRelated: Improved spectroscopes made Fraunhofer’s wavelength measurements possible.
Norman LockyerRelated: Advances in spectroscopes made Lockyer’s study of solar lines possible.
William HugginsRelated: Huggins used spectroscopes to examine light from stars and nebulae.