Analysing the Evidence


To display and analyse your image data files you will use a special piece of image processing software called LTImage.

Take the following steps . . .

LTImage Screenshot

LTImage Screenshot

  1. Using image processing software

    Run LTImage in a new window on your computer desktop alongside this planet investigation.

    Load your image data file of the planet observation by selecting FILE (menu) and then OPEN DATA IMAGE (option).

    If you have not downloaded, or are not sure how to use LTImage, click HERE.

    Firstly, identify the time the observation was carried out by the telscope.

    To do this click on Astro (menu), Image Properties (option) and Calibration (button on right) and you will be able to find out this information.

  2. Measuring the diameter of your planet

    Measuring Planet

    Measuring the Planet

    • Select IMAGE (menu) and then EXAMINE (option)

    • Click somewhere on the image of the planet.

      Note that the pointer X and Y co-ordinates are displayed under the "Examine Image box" on the right of the screen.

      • For accurate measurements magnify the planetary image by clicking on DISPLAY (menu) and then ZOOM+ (option) a number of times.


    • Click on the left hand limb of the planet (see diagram) and note down the X and Y co-ordinates in a table similar to the one shown here.

      • Limb of
      planet      		 X Y
      Left  
      Right  


    • Keeping the Y co-ordinate the same as before, click on the right hand limb of the planet.

      Note the new X co-ordinate.

    • Calculate the difference between the two values of X.

      This is the diameter of the planet in pixels, and you should note it down.

      Pixels are NOT a measure of distance.

    • You now have to convert pixel size into kilometres to find the real size of the planet.

      The number of kilometres represented by ONE PIXEL must now be found.

      This can be done by clicking on ASTRO (menu), IMAGE PROPERTIES (option) and then CALIBRATION (button on right). You will see Pixel scale (at the object) displayed with a value for this observation.

      Multiply the pixel scale by the number of pixels across the planet and you will have a value for distance in kilometres.

  3. Improving the accuracy of your result

    To get a more accurate result, you could repeat the measurement a number of times and take the average value. If you have time, you could even take a series of images of the same planet over a few weeks and again take the average value of your measurements.

    4. Now you must evaluate your evidence . . .


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