Task: conterr Purpose: Continuum subtraction error estimate, when using UVLIN. Categories: uv analysis Given an image of the continuum in a spectral line experiment, CONTERR estimates the residual continuum artifacts that will be present after continuum subtraction using UVLIN. The results are intended to be indicative, rather than rigorously accurate. The peak value and location of the errors are approximately correct, but the actual error pattern will differ significantly from that presented here. This task essentially just evaluates the expressions given in Table 1 of "An analysis of visibility-based continuum subtraction" by Bob Sault. CONTSEN makes plots of noise amplification factor of tasks such as UVLIN, AVMATHS, and CONTSUB. Key: in An estimate of the continuum. It should be either a dirty image or a deconvolved/restored image. No default. Key: order The order of the polynomial fit in UVLIN, either one or two numbers can be given. If two, then CONTSEN determines the error for order(1) to order(2) inclusive. The default is to determine the noise sensitivity for first order only. Key: bw Total spectral bandwidth, in GHz. Default is 0.008 (i.e. 8 MHz). Key: fwhm The image resolution, given as the FWHM of the corresponding gaussian, in arcsec. This is the same as the FWHM that RESTOR would determine. The default is to get the information from the input image. Two values can be given, being the FWHM in x and y respectively (i.e. the position angle is assumed to be along one of these axes). If only one value is given, the gaussian is assumed to be circularly symmetric. Note that high order fits are very sensitive to this parmeter. Key: out An output image containing the error images. The default is no output image. Key: options Extra processing options. Several can be given, separated by commas. Minimum match is used. Possible values are: shift Determine an optimum shift of the phase centre to be applied before the error is evaluated. This shift will minimise the error in some sense. Revision: 1.6, 2021/06/02 04:45:09 UTC

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