The Ginga display GUI is used to display and analyze DEIMOS mosaic images in real time while you are observing. An alternative tool to open DEIMOS mosaic images offline is the script ds9_mosaic image_name, which can be used on any polo or deimos (local) terminal.

The following figure shows the layout of the DEIMOS Ginga display GUI:

Ginga is a very versatile FITS image viewer, but in practice, only a few options are needed when observing:

• Channels: There are two display channels, Raw and Other. The images are displayed in real time on the Raw channel. This can be selected by clicking on the Raw tab at the top of the main display area.
• Contrast control: The image contrast can be controlled by manipulating the cut levels on the synopsis panel on the lower-left area of the GUI:
  • Cut low: It is set to 0 by default, because the counts on the detector gaps is 0. However, the best contrast results can be obtained by using a cut low of 950 counts.
  • Cut high: This can be adapted to the type of frame that is being displayed. For instance, for an internal flat, a value of 55000 counts is appropriate. For a spectrum of a science target on sky, a value of 3000 or 5000 counts is probably more apropriate.
  Once the cut low and high values are set, click on Cut Levels to update the display.
  One can also let Ginga define the contrast levels automatically with the Auto Levels button. Not that this will automatically set the cut low to 0.
  The contrast can be controlled dynamically by holding the Ctrl key, right click on the mouse and drag over the main display area. Note, on some computers the Ctrl and the R key must be held simultaneously for for the dynamic contrast to work.
• Projection plots: To make a projection plot on the current image, select the channel at the bottom of the main display area, then click on Operations → Analysis → Cuts:
  • To make a new projection: Right-click and drag on the image. Release the mouse button once you are happy with the selection
  • To move an existing projection: Left-click where you would like to place the projection on the image.

Please, visit the Ginga image viewer homepage and the Ginga quick reference for more information.