beam2bl
Since the SH Transform of an arbitrary beam is
then, for a circular beam
where P_{l} 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) |
plot, bl1-bl |
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