code: def sky2pix_vec(self, pos, r, pa):
          
          ra, dec = pos
          x, y = self.sky2pix(pos)
          a = translate(ra, dec, r, pa)
          locations = self.sky2pix(a)
          x_off, y_off = locations
          a = np.sqrt((x - x_off) ** 2 + (y - y_off) ** 2)
          theta = np.degrees(np.arctan2((y_off - y), (x_off - x)))
          return x, y, a, theta
docs: Convert a vector from sky to pixel coords.
          The vector has a magnitude, angle, and an origin on the sky.
  
          Parameters
          ----------
          pos : (float, float)
              The (ra, dec) of the origin of the vector (degrees).
  
          r : float
              The magnitude or length of the vector (degrees).
  
          pa : float
              The position angle of the vector (degrees).
  
          Returns
          -------
          x, y : float
              The pixel coordinates of the origin.
          r, theta : float
              The magnitude (pixels) and angle (degrees) of the vector.