Spectral resolution

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

Additional recommended knowledge

What is the Correct Way to Check Repeatability in Balances?

Guide to balance cleaning: 8 simple steps

What is the Sensitivity of my Balance?

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.

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.

References

Hatim

1. Kim Quijano, J., et al. (2003), STIS Instrument Handbook, Version 7.0, (Baltimore: STScI)