Interstellar Extinction

Joachim Köppen Kiel Apr.2017

This utility computes the interstellar extinction for any wavelength, based on extinction laws by various authors. The values can be displayed as the attenuation exp(-tau) the optical depth tau at that wavelength, the attenuation in magnitudes A(λ) = -2.5 log10(exp(-tau)), and in the form of the function f(λ) = (tau(λ)/tau(4861)-1). The selective extinction E(B-V) = A(B)-A(V), the ratio of total to selective extinction R = A(V)/E(B-V), and the logarithmic extinction at Hβ c with exp(-tau(4861 Å)) = 10^(-c) (used for emission line spectra), are given or can be entered.

Hit the Enter key after making an entry. This will mark this field by a light green background and as the field of the last entry. Note that for Cardelli99 and FitzPatrick99 one can also change the value of R.

The Band and Wavelength fields accept the usual designations: U, B, ... , N, Q, u, b, y, Hbeta, Halfa, Halpha, and numerical values in Ångstroem, or micrometres followed by the letter u.

If the display shows ---- instead of a value, it means that the chosen extinction law does not cover that wavelength.

Extinction Law:

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