Spectral resolution
From Wikipedia, the free encyclopedia
The spectral resolution or resolving power of say a spectrograph, or, more generally, of a frequency spectrum, is a measure of its power to resolve features, say in the electromagnetic spectrum. It is usually defined by
R = λ / Δλ,
where Δλ is the smallest difference in wavelengths that can be distinguished, at a wavelength of λ. So, for example, the Space Telescope Imaging Spectrograph (STIS) can distinguish features 0.17 nm apart at a wavelength of 1000 nm, giving it a resolving power of about 5,900. An example of a high resolution spectrograph is the Cryogenic High-Resolution IR Echelle Spectrograph (CRIRES) installed at ESO's Very Large Telescope, it has a spectral resolution of up to 100,000[1].
The spectral resolution can also be expressed in terms of physical quantities, say velocity; then it describes the difference between velocities Δv that can be distinguished through the Doppler effect. Then, the definition is
R = c / Δv,
where c is the speed of light. The STIS example above then has a spectral resolution of 51 kilometres per second.
[edit] References
- Kim Quijano, J., et al. (2003), STIS Instrument Handbook, Version 7.0, (Baltimore: STScI)
