Making an RGB Color Image

Accessing DS9 software

  • Launch the TU Science Desktop. (See instructions under the Simulations and Software section of this Bb site.)
  • Open the ASTR folder on this desktop.
  • Launch SAOImage DS9

Creating the RGB Image

  • Download the FITS images you are analyzing onto the Science Desktop.
  • From the top menu, go to FrameNew Frame RGB. This will create a blank frame in the main DS9 window and a separate small RGB window that shows buttons for the red, green and blue images. By default, the current frame is set to Red.
  • Load the red image: File Open and FITS file taken in the R filter. When the image loads, you likely won’t see anything because the display is washed out. We’ll need to adjust the brightness range and contrast.
  • Set Scale on the menu to Square Root, then select Scale5%. You should see something now! This sets up the display so you can now see 99.5% of all the pixel brightnesses in the image.
  • Zoom out so you can see the whole image.
  • Now, right-click and hold the mouse button while panning over the image to adjust the contrast. Keep panning and moving the cursor around until the nebula looks red and the surrounding sky nearly black.
  • Next, go to the separate RGB window and set the current frame to Green. Load the G filter image by clicking FileOpen and then setting the same display scale (Square Root, 5%) and right-click panning your cursor until you see the green from the nebula, but the sky around it is almost black.
  • Next, click on Blue in the RGB window, and load B filter image. Scale and adjust the contrast on this image to also display with the surrounding sky black.

Voila! You now have a beautiful color image just like what you see online! There’s a lot more image processing to do to get this image ready for public release, but you are ready to direct your attention to the image details.