The observation of a rotating body using high-resolution spectroscopy

Abstract

If a high-resolution specotroscopic instrument is used to observe a rotating body in the light from a narrow spectral line, significant factors affect the apparent field of view when both the line width and the instrumental resolution, expressed as their equivalent Doppler velocities, are less than, or comparable to, the surface velocity of the observed body. The particular case of the Sun observed with the Birmingham resonant scattering spectrometer is considered, and the effect on the apparent velocity oscillations produced by supergranulation is discussed.