title: Overlapping polar countourf and scatter plot
body: <p>Thanks to this very helpful <a href="https://stackoverflow.com/questions/9071084/polar-contour-plot-in-matplotlib-best-modern-way-to-do-it">post</a>, I finally figured out how to make a polar filled-contour plot. However, when I moved to the next step and tried to add a scatter point to the same plot, I ran in some problems. Here is the original script:</p>
  
   <pre class="lang-py prettyprint-override"><code>import numpy as np
  import matplotlib.pyplot as plt
  
  #-- Generate Data -----------------------------------------
  # Using linspace so that the endpoint of 360 is included...
  azimuths = np.radians(np.linspace(0, 360, 20))
  zeniths = np.arange(0, 70, 10)
  
  r, theta = np.meshgrid(zeniths, azimuths)
  values = np.random.random((azimuths.size, zeniths.size))
  
  #-- Plot... ------------------------------------------------
  fig, ax = plt.subplots(subplot_kw=dict(projection='polar'))
  ax.contourf(theta, r, values)
  
  plt.show()
  </code></pre>
  
  <p>Which produced this image:
  <img src="https://i.stack.imgur.com/k9tC4.png" alt="Polar filled contour without scatter"></p>
  
  <p>If I add also a scatter plot:</p>
  
  <pre class="lang-py prettyprint-override"><code>#-- Plot... ------------------------------------------------
  fig, ax = plt.subplots(subplot_kw=dict(projection='polar'))
  ax.contourf(theta, r, values)
  ax.scatter(np.radians(140), 40, s=20, c='White')
  </code></pre>
  
  <p>I get instead this image:</p>
  
  <p><img src="https://i.stack.imgur.com/BDkW8.png" alt="Polar filled contour with scatter"></p>
  
  <p>Why do I get the thick white border between the filled contours and the axes? How do I get rid of it?</p>
  
  <p>Thank you very much!</p>