85
Cannon in the 1890s and early 1900s), Secchi remains a major pioneer of stellar
classification, having developed a method that is still crucial in astrophysics.
6
Secchi’s recognition of the absorption bands of carbon in the spectra of some
stars is of particular importance. He is thus the discoverer of carbon stars, the fourth
6 See, e.g., Hoffleit 1991, Kaler 1989, and Hearnshaw 1986: 57–66, McCarthy 1950, 1994, especially on Secchi’s contributions.
Fig. 5.1 (a) The second spectroscope that Secchi used 1863–1866. This direct-vision spectroscope has a 5-prism train P of three crown glass and two flint glass prisms, slit s and a collimator
lens C. Comparison light could be led in by the small prism r from the side S. This prism absorbed
much light, a disadvantage with faint starlight. From http://www.antique- microscopes.com/chemistry/Hofmann_direct_vision_spectroscope.htm; see also Secchi 1872: 413
(b) Secchi’s third spectroscope with three prisms, attached to the Merz refractor of 25 cm aperture.
Since this optimized instrument absorbed less light, Secchi could observe spectra of stars up to
seventh and eighth magnitude. Copy of an engraving by Pierre Edelestand Stanislas Dulos
(1820–74), on Dulos see Hentschel 2001 and the DSI entry http://www.uni- stuttgart.de/hi/gnt/
dsi2/index.php?table_name=dsi&function=details&where_field=id&where_value=526.
From
Secchi 1875-I: 229; see also Secchi 1872: 228, Chinnici 2017: 58
(c) Secchi’s fourth instrument—an objective prism with a refracting angle of 12° in its mounting
frame, to be attached to the Merz refractor in front of the objective (25 cm aperture). With this
instrument, Secchi observed thousands of stellar spectra. From Merz 1870, reproduced with commentary in Chinnici 2017: 55
5 Angelo Secchi, Stellar Spectroscopy, Solar Physics, and Visual Science Culture
Cannon in the 1890s and early 1900s), Secchi remains a major pioneer of stellar
classification, having developed a method that is still crucial in astrophysics.
6
Secchi’s recognition of the absorption bands of carbon in the spectra of some
stars is of particular importance. He is thus the discoverer of carbon stars, the fourth
6 See, e.g., Hoffleit 1991, Kaler 1989, and Hearnshaw 1986: 57–66, McCarthy 1950, 1994, especially on Secchi’s contributions.
Fig. 5.1 (a) The second spectroscope that Secchi used 1863–1866. This direct-vision spectroscope has a 5-prism train P of three crown glass and two flint glass prisms, slit s and a collimator
lens C. Comparison light could be led in by the small prism r from the side S. This prism absorbed
much light, a disadvantage with faint starlight. From http://www.antique- microscopes.com/chemistry/Hofmann_direct_vision_spectroscope.htm; see also Secchi 1872: 413
(b) Secchi’s third spectroscope with three prisms, attached to the Merz refractor of 25 cm aperture.
Since this optimized instrument absorbed less light, Secchi could observe spectra of stars up to
seventh and eighth magnitude. Copy of an engraving by Pierre Edelestand Stanislas Dulos
(1820–74), on Dulos see Hentschel 2001 and the DSI entry http://www.uni- stuttgart.de/hi/gnt/
dsi2/index.php?table_name=dsi&function=details&where_field=id&where_value=526.
From
Secchi 1875-I: 229; see also Secchi 1872: 228, Chinnici 2017: 58
(c) Secchi’s fourth instrument—an objective prism with a refracting angle of 12° in its mounting
frame, to be attached to the Merz refractor in front of the objective (25 cm aperture). With this
instrument, Secchi observed thousands of stellar spectra. From Merz 1870, reproduced with commentary in Chinnici 2017: 55
5 Angelo Secchi, Stellar Spectroscopy, Solar Physics, and Visual Science Culture