Astronomy

Unpacking starlight with a grating

Send light through a slit and diffraction grating onto a detector. Change groove density, illuminated width and radial velocity to separate resolution from Doppler shift.

By Mykhailo Makarov

Actual application image

The model and its limits

First-order normal-incidence grating equation, a Gaussian instrumental line profile and nonrelativistic Doppler shift. Slit broadening is specified directly in nm. Beam spread and detector line width are magnified for readability.

Equations used in the module

Equations
sin β = λ/d; resolving power = mN; Δλ/λ = v/c; FWHM² = (λ/R)² + slit².

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