Using Rigil (Alpha Centauri) the animation shows how the H-alpha line of a stationary star periodically shifts over the course of a year due to Earth's orbit.

If one plots the redshift—or radial velocity—as a function of the observation time (for instance, using a spreadsheet), a sinusoidal pattern becomes apparent that can be fitted with a period of 365.25 days.

Furthermore, a vertical shift is observed that corresponds to the radial velocity of the observed star.

While the star's H-alpha line shifts over the course of the year, the oxygen (O2) lines of Earth's atmosphere remain constant.

The difference between spectral classes O, A, F, and M is evident in the example of the Mg triplet. The quality of the NRES spectra is demonstrated by a comparison of Mintaka O9 (blue), Vega A0 (orange), Procyon F5 (green), and Antares M1 (red).

This GIF animation can be created from NRES files with just a few clicks, offering students a quick, engaging overview.

The examination of additional prominent lines, as well as the width of these lines, allows for the relatively precise classification of unknown stars into spectral classes.

Using Mizar A (Zeta Ursae Majoris) as an example, one can observe the splitting of the Hα line in spectroscopic binaries:

All stellar lines undergo the same splitting, while the telluric lines remain static (cf. Point 1).

The example of Deneb (Alpha Cygni) illustrates an A2 Ia star that, at irregular intervals, sheds portions of its hydrogen envelope. Since this envelope is excited to luminescence by the hot central star, the portion receding from us produces a redshifted emission line against the dark background. Conversely, the bright starlight penetrates the hydrogen envelope approaching us, resulting in a blueshifted absorption line.

Outbursts from Deneb, as well as changes in the velocity of the hydrogen, can be easily measured.

VV Cephei is a variable binary star system, classified as an eclipsing variable. The primary star—a red supergiant (VV Cephei A)—is in a late, unstable evolutionary stage and is extremely distended. Due to the close proximity between the two components, the red supergiant exceeds its Roche limit, causing matter to flow onto its smaller, blue companion (VV Cephei B) in the form of an accretion disk.

The NRES spectrum reveals the Hα emission lines of this luminous accretion disk: the portion of the disk moving away from us exhibits a redshift, while the portion approaching us is blueshifted. At the center of this profile, the light from the blue companion is absorbed by the hydrogen within the accretion disk.

Using Mizar A (Zeta Ursae Majoris) as an example, one can observe the splitting of the Hα line in spectroscopic binaries:

All stellar lines undergo the same splitting, while the telluric lines remain static (cf. Point 1).