Topic outline

  • SPN Activity 1: Viewing and Processing Images from the Liverpool Telescope

    The NSO's very own LTImage is an image processing tool that allows users to view and analyse images from the Liverpool Telescope.

    When the NSO was being developed, it was decided that the freely available image processing software was too complex for use in schools. As such, we decided to create our own software, which aims to simplify the process of analysing image data from astronomical telescopes.

    LTImage can work with all image data that are in the FITS image format. This means that it can work with images from most professional telescopes around the world.

    Read on to find out more about FITS files and how you can view and process them.

  • FITS Files

    FITS with ImageWhat are FITS files used for?

    Astronomers use telescopes all over the world and even in space. Although every telescope is different, the image data that they create is very similar.

    In order to make it easier to use lots of different telescopes, astronomers decided to create a particular kind of computer file that all telescopes could use. They called this kind of file a FITS file, which stands for the Flexible Image Transport System.

    As well as storing the actual images, the files also have other information in them, such as the date and time of the observation, the name and location of the telescope, the weather at the time of the observation and so on.

    There are now large archives of FITS files, bringing together observations from many telescopes and allowing astronomers to make use of millions of images.

    The difference between FITS files and images from a digital camera

    Astronomical FITS files are not like JPEGs or other common image file formats. FITS files accurately record the intensity of the light that fell on each pixel of the telescope camera, and this can confuse people who are new to using these files.

    The JPEGs that come from ordinary digital cameras and phones with cameras are actually quite highly processed by the time you see them. The electronics of the camera takes the images recorded and processes it in a way that give you an acceptable image to view immediately.

    With FITS files there is generally no automated processing as this would destroy the very data that we are interested in a scientists. This means that often when a FITS file is displayed in software such as LTImage you don't immediately get a recognisable image. In fact, unless you have an image of something quite bright like a planet or the Moon, you may not see very much at all.

  • Viewing FITS Files

    To see your image you need to "scale" the brightness values, and LTImage (and other FITS processing software) lets you do this.

    The image below of M1 -The Crab Nebula shows that before processing only a few bright stars are visible. After processing a lot more detail in the nebula can be seen.

    M1 Before and After

    • Before you go further, we recommend that you download LTImage using the link below. In the following sections and other courses you will be encouraged to use this software so it is worth downloading it now.

    • LTImage doesn't require any installation, and can be run from a USB stick. This makes it ideal for computers where you do not have permission to install software. It can also be copied to a shared drive on a network and computers on the network can access it from there.

  • Using LTImage to View Your Images

    LTImage ScalingActivity

    We hope that you have some images of your own that you have requested from the Liverpool Telescope, but if you haven't you will find a link to some example files below.

    1. Log in to your NSO account and go to the My Observations page.

    2. Click on the observation code (left column) for any of your observations that have the status "Read to Download".

    3. The next page will give you some information about your observation, and a link to go to the page where you can download your image. Click on this link. (The image displayed on this page is not your observation, but an archive image of this astronomical object.)

    4. At the bottom of the page you will see a link "FITS File", use this link to download your file to your computer.

    5. Using LTImage, and the help below, process your image and save it as a JPEG file.

    Using LTImage to Process FITS files

    To make it easier for you to follow the steps in processing your FITS files, we have created a screencast showing how you can do this.

    View the Video Screencast Now

    If you are using a tablet device without a Flash Player, please use the link below.

    MP4 Video Screencast File

    Please Note: the screencast shows the final image being saved as a BMP (bitmap) file. The current version of LTImage also allows files to be saved as JPEGs and this may be preferable for some uses of the images, such as on websites. JPEG images use compression to make the file size smaller, if you want to ensure you have the highest quality images, please use the BMP option.

    • In case you don't have any of your own images from the Liverpool Telescope, we have provided some example images below. You might find it easier to right click on the files to save them to a location of your own choice.

  • Suggested Things To Do Next

    Now that you know how to make your images viewable using LTImage, you can get your own observations from the Liverpool Telescope and view and process those.