def px2hc(xpx, ypx, dx, dy, xc, yc, sz):
    """
    Given positions in pixel coordinates (x = [0->nx-1]; y = [0->ny-1]),
    determine the HC x and y coordinates in arcseconds.
    - xpx, ypx = pixel coordinates of AR positions
    - dx, dy = arcsec/px
    - xc, yc = FOV center in arcsec from solar disk center
    - xs, ys = x and y px size of the image
    """
    xs = sz[0]
    ys = sz[1]
    hcx = ((xpx - (xs/2.))*dx) + xc
    hcy = ((ypx - (ys/2.))*dy) + yc
    return hcx, hcy