diff --git a/docs/wcs_utils.rst b/docs/wcs_utils.rst index f267399a6..950e42be4 100644 --- a/docs/wcs_utils.rst +++ b/docs/wcs_utils.rst @@ -7,9 +7,9 @@ between air and vacuum, as well as a function for calculating the refractive ind of air, which is used in the air to vacuum conversions. There are multiple methods available for the refractive index calculation, most of which agree with each other to a high level of precision. However, the Griesen (2006) equation seems to have a small -offset from the others (see plot below) and thus in specutils 1.17.0 we have changed -from using that method as the default to using the Morton (2000) equation, which is -consistent with the IAU standard. +offset from the others of about 0.07 Angstrom (at the wavelengths shown in the plot below) +and thus in specutils 1.17.0 we have changed from using that method as the default to +using the Morton (2000) equation by default, which is consistent with the IAU standard. .. image:: air_to_vac_offset.png :alt: Results of air to vac conversion at optical wavelengths. @@ -32,3 +32,4 @@ Reference/API :skip: GWCS :skip: Shift :skip: Tabular1D + :skip: SpectralGWCS diff --git a/specutils/utils/wcs_utils.py b/specutils/utils/wcs_utils.py index ae7b01994..e064aaf73 100644 --- a/specutils/utils/wcs_utils.py +++ b/specutils/utils/wcs_utils.py @@ -85,7 +85,8 @@ def refraction_index(wavelength, method='Morton2000', co2=None): UV. 'Griesen2006' gives values that are slightly inconsistent with the other methods (~0.07 Angstrom difference at visible wavelengths), but it is the best option in the FUV due to the mathematical singularities in the others. - See https://github.com/astropy/specutils/issues/1162 for more detail. + See https://specutils.readthedocs.io/en/latest/wcs_utils.html for more detail, or + https://github.com/astropy/specutils/issues/1162 for additional context. co2 : number, optional CO2 concentration in ppm. Only used for method='Ciddor1996'. If not @@ -162,15 +163,17 @@ def air_to_vac(wavelength, scheme='inversion', method='Morton2000', co2=None, How to convert from vacuum to air wavelengths. Options are: * 'inversion' (default) - result is simply the inversion (1 / n) of the - refraction index of air. Griesen et al. (2006) report that the error - in naively inverting is less than 10^-9. + refraction index of air. Griesen et al. (2006) report that the error + in naively inverting is less than 10^-9. + * 'Piskunov' - uses an analytical solution derived by Nikolai Piskunov - and used by the Vienna Atomic Line Database (VALD). + and used by the Vienna Atomic Line Database (VALD). + * 'iteration' - uses an iterative scheme to invert the index of refraction. method : str, optional Only used if scheme is 'inversion' or 'iteration'. One of the methods - in refraction_index(), default is 'Morton2000' + in `~specutils.utils.wcs_utils.refraction_index`, default is 'Morton2000' co2 : number, optional Atmospheric CO2 concentration in ppm. Only used if scheme='inversion' and