Spectrum of Vega using CCDSPEC and QHY6 camera

Manually guided, 30 sec exposure in Nebulosity 4 with QHY6 camera, Sky Watcher 80mm Equinox Pro on manual alt-az Manfrotto mount.

Before anyone asks, I could not find the Ring Nebula tonight in the guide eyepiece on the CCDSPEC!

From RIchard Walk’s book, “Spectral Atlas for Amateur Astronomers”, Vega is a Lamba Bootis Class star. Stars of this class are classified according to their H-Balmer lines approx. on main sequence within spectral types F0-A0. Striking here is a generally weak metal-line spectrum with the main feature of Mg II absorption at 4481 A (448.1nm). This line is shown well on my spectra of Vega below as are the H-Balmer lines.

The following is from Wikipedia (https://en.wikipedia.org/wiki/Balmer_series):

The Balmer series is characterized by the electron transitioning from n ≥ 3 to n = 2, where n refers to the radial quantum number or principal quantum number of the electron. The transitions are named sequentially by Greek letter: n = 3 to n = 2 is called H-α, 4 to 2 is H-β, 5 to 2 is H-γ, and 6 to 2 is H-δ. As the first spectral lines associated with this series are located in the visible part of the electromagnetic spectrum, these lines are historically referred to as “H-alpha”, “H-beta”, “H-gamma” and so on, where H is the element hydrogen.

Transition of n 3→2 4→2 5→2 6→2 7→2 8→2 9→2 ∞→2
Name H-α / Ba-α H-β / Ba-β H-γ / Ba-γ H-δ / Ba-δ H-ε / Ba-ε H-ζ / Ba-ζ H-η / Ba-η Balmer break
Wavelength (nm) 656.45377[2] 486.13615[3] 434.0462[3] 410.174[4] 397.0072[4] 388.9049[4] 383.5384[4] 364.6
Energy difference (eV) 1.89 2.55 2.86 3.03 3.13 3.19 3.23 3.40
Color Red Aqua Blue Violet (Ultraviolet) (Ultraviolet) (Ultraviolet) (Ultraviolet)

The familiar red H-alpha spectral line of the Balmer series of atomic hydrogen, which is the transition from the shell n = 3 to the shell n = 2, is one of the conspicuous colours of the universe. It contributes a bright red line to the spectra of emission or ionisation nebula, like the Orion Nebula, which are often H II regions found in star forming regions. In true-colour pictures, these nebula have a distinctly pink colour from the combination of visible Balmer lines that hydrogen emits.


Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.