title: Orthographic camera positioning
body: <p>I've created a scene of a huge spherical star field using units of lightyears and I want an orthographic camera positioned so it is looking at the origin and is viewing only 15 lightyears accross.
  I'm currently using the following code to construct the camera but the scene appears quite small and far away, I can see the entire star field:</p>
  
  <pre><code>new THREE.OrthographicCamera( window.innerWidth / - 2, window.innerWidth / 2, window.innerHeight / 2, window.innerHeight / - 2, -500, 1000 );
  </code></pre>
  
  <p>How can I construct this camera to only show a close up section of the scene? (I'll worry about not rendering stars outside this view later)</p>