<sect1 id="tool-eyepieceview">
<title>Simulate Eyepiece View</title>
<indexterm><primary>Tools</primary>
<secondary>Simulate Eyepiece View</secondary>
</indexterm>

<screenshot>
<screeninfo>
Simulate eyepiece view
</screeninfo>
<mediaobject>
  <imageobject>
    <imagedata fileref="EPView_Screenshot.png" format="PNG"/>
  </imageobject>
  <textobject>
    <phrase>
        Example View
    </phrase>
  </textobject>
  <caption>
      On the left hand side is the sky map shot from &kstars;. On the right hand side is the POSS (DSS) image of the same region. The orientation in the above example has been adjusted to match the view through a Dobsonian telescope at the location and time of the simulation in &kstars;.
  </caption>
</mediaobject>
</screenshot>

<para>
This tool simulates how an object looks through your eyepiece. In addition to rendering the eyepiece field, &kstars; can also fetch and overlay the DSS imagery. Additionally, if you are using a Dobsonian telescope, you can rotate the field of view to match the eyepiece view.
</para>

<para>To use this feature, first define your eyepieces' fields of view using the <link linkend="customize">FOV Symbol editor</link>.</para>

<para>Then there are two ways to invoke the feature:
<itemizedlist>
    <listitem><para>In Sky Map, right click on the desired object and click <guilabel>Simulate eyepiece view</guilabel> in the popup menu.</para></listitem>
    <listitem><para>In observation planner, right click an object and click <guilabel>Simulate eyepiece view</guilabel> in the popup menu.</para></listitem>
</itemizedlist>
</para>

<para>When the tool is first invoked, it will prompt a dialog to select the desired FOV to render the view. To compare the rendered view against a real sky image, click the <guibutton>Fetch DSS image</guibutton> button to download a DSS image. You can manually adjust the view to match your eyepiece using the rotation slider, the <guilabel>Invert view</guilabel> and <guilabel>Flip view</guilabel> check boxes. Alternatively, you can use a pre-calculated amount of rotation by using one item of the <guilabel>Preset:</guilabel> dropdown box that is tailored for different optical systems.</para>

<screenshot>
<screeninfo>
Arp84 eyepiece view
</screeninfo>
<mediaobject>
  <imageobject>
    <imagedata fileref="Arp84_EyepieceView.png" format="PNG"/>
  </imageobject>
  <textobject>
    <phrase>
        View with Overlay
    </phrase>
  </textobject>
  <caption>
      Arp84 eyepiece view with ticks enabled indicating how the chart must be oriented to match the eyepiece view through a Dobsonian at a given time (the generated data is for location McDonald Observatory Texas, and the date is 14th Dec 2016).
  </caption>
</mediaobject>
</screenshot>

<para>
To export the view to a file, click <guibutton>Export</guibutton> button. Export enables adding ticks for printed charts as shown above and save the image.
</para>

</sect1>
