Since the SH Transform of an arbitrary beam is
where Pl is the Legendre Polynomial, b(l) is the beam window (or transfer) function returned by beam2bl and is the beam radial profile expected as input of beam2bl.
IDL's routine INT_TABULATED is used to perform the integration.
|bl = gaussbeam(15.d0, 4000, 1)|
|theta = dindgen(4000)/100.|
|beam = bl2beam(bl, theta, /arcmin)|
|bl1 = beam2bl(beam, theta, 4000, /arcmin)|
the example above generates a beam window function (defined for all l in ) for a 15arcmin-FWHM gaussian beam, computes the beam profile for angles in [0,40] arcmin, computes back the beam window function from the beam profile and finally plots the difference between the beam window functions.
Version 3.31, 2017-01-06