Astronomical Spectra

Some years ago, in the mid 70's, I built two spectrographs for taking astronomical spectra. The first one utilized a homemade liquid prism for dispersion. It worked quite well, and by changing the liquid, I got different dispersions to work with. Later on I built a more compact unit, where I used either a reflection grating or a glass prism. The grating had 1200 lines/mm, and gave a higher degree of dispersion than the prism. For the Sun and Moon and the very brightest stars, I used the grating. For less bright objects, the grating was exchanged for the prism.

A. Spectrum of Vega
B. Spectrum of Arcturus
C. Spectrum of the Sun, blue part
D. Spectrum of the Sun, red part
E. Spectrum of Nova Cygni 75

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A. Spectrum of VEGA, a type A0 star. Photo 1978-08-20. Prism.

The spectrum of Vega, alfa Lyrae, is typical of an A0-star. The Balmer series of absorption lines is very prominent. The spectrum was taken with a prism installed.

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B. Spectrum of Arcturus, Alfa Bootis, K2 III. Prism.

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C. The Sun, spectrum in the green to violet region. Grating.

I-- detail A --I I-- detail B --I

Below: Detail A. The Magnesium and Iron lines, b1, b2 and b4.

Below: Detail B. The Calcium lines in the violet end of the spectrum are very characteristic in the solar spectrum.

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D. The Sun, spectrum in the red to green region. Grating.

I-- detail C --I .

Below: Detail C. The Sodium lines D1 and D2 with about 6 Angstrom separation.

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E. Nova Cygni 75 (september 1975), liquid prism.

Above: The very bright nova that appeared in Cygnus in september 1975 showed very nice emission lines the first weeks after its outburst. These came from the fast expanding shell around the nova. I photographed the spectrum with my first spectrograph, and although it was primitive, the spectrum turned out fine.

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