ism3d.uvhelper.ft.advise_imsize

ism3d.uvhelper.ft.advise_imsize(u, v, pb=0, f_min=5.0, f_max=2.0, even=True)[source]

Compute the recommended image size given the (u, v) locations. Typical call signature:

nxy, dxy = advise_imsize(u, v, PB=0, f_min=5., f_max=2.5, verbose=False)
Parameters

  • u (array_like, float) – u coordinate of the visibility points where the FT has to be sampled. units: wavelength

  • v (array_like, float) – v coordinate of the visibility points where the FT has to be sampled. The length of v must be equal to the length of u. units: wavelength

  • PB (float, optional) – Primary beam of the antenna, e.g. 1.22*wavelength/Diameter for an idealized antenna with uniform illumination. units: rad

  • f_min (float) – Size of the field of view covered by the (u, v) plane grid w.r.t. the field of view covered by the image. Recommended to be larger than 3 for better results. units: pure number

  • f_max (float) – Nyquist rate: numerical factor that ensures the Nyquist criterion is satisfied when sampling the synthetic visibilities at the specified (u, v) locations. Must be larger than 2. The maximum (u, v)-distance covered is f_max times the maximum (u, v)-distance of the observed visibilities. units: pure number

  • verbose (bool, optional) – If True, prints information on the criteria to be fulfilled by nxy and dxy.

Returns

  • nxy (int) – Size of the image along x and y direction. units: pixel

  • dxy (float) – Returned only if not provided in input. Size of the image cell, assumed equal and uniform in both x and y direction. units: cm