FITS

FITS File Format

The images that you will take using iTelescope.net are stored in a file format that you likely haven't seen before. You may be familiar with examples of image file formats such as JPEG, GIF, PNG, or BMP, all of which which are standardized ways of organizing and storing digital images. Data from iTelescope.net is stored in a format called Flexible Image Transport System, or FITS. FITS is the most commonly used digital file format in astronomy. You will be using the same type of files that astronomers work with every day!

FITS files are a convenient way of storing astronomical data because they are capable of storing more than just image files. Other non-image data can be stored in a FITS file, including spectra. At the start of every FITS file there is a header, which contains information about the image that includes the data the image was taken, what telescope was used to obtain the image, how long the exposure time was, and more. The header can also contain information about the coordinates of the objects in the images. FITS files are also capable of storing higher quality image information than JPEGs. In particular, they are able to store a much larger range of brightness values than JPEGs are able to, which means that both bright and faint objects can be seen in better detail.

Although FITS files are very common in astronomy, they are not very common outside of the field. A consequence of this is that most of the common image manipulation software packages (including Photoshop) cannot be used to open or manipulate FITS files. There are a variety of FITS image viewers and manipulation tools available for download. One such tool is Nebulosity, which is capable of reading, displaying, manipulating, and saving FITS files. Other common tools include ds9 and fv.