Documentation on impoly

Task: impoly
Purpose: Flat field subtraction using a 2D polynomial fit
Categories: map combination

        IMPOLY (IMage POLYnomial subtraction) is a MIRIAD task which
        applies a specified x-y region of each plane of a cube
        to a polynomial least squares fit, and subtracts the fit, 
        from across the region, across the entire plane.

Key: in
        The input image. No default.

Key: out
        The output image. No default.

Key: order
        The degree of the highest term of the polynomial fit. 
        It is not possible to have a different order of the polynomial 
        in X and Y. Default is zero: the fit to a constant.

Key: coeffs
        A logical, specifying whether you want to see fitted polynomial
 	coefficients. Default: no.
        Note: the coefficients are defined w.r.t. the reference pixel,
        and are in pixel units.

Key: region
        Full region specifications are supported.
        Default: the entire image.