Making a color composite image from individual R, G, B images

+ + =

During the workshop, we acquired images of the Eta Carinae Nebula from a telescope in Australia. Here are JPEG versions of the images taken through R (red), G (green) and B (blue) filters.

There are many tools which can combine three individual images into a single color (RGB) composite image.

I use the image processing program called GIMP , which is a free, open-source program; it runs under Windows, or Mac OS, or Linux. I followed the instructions given at this page ; I had to make a few changes because the "Colorify" command was in a different menu on my (old) version of Gimp.
Aaron Titus' tips for using ImageJ to create color composites
Larry Marschall recommends using Photoshop: one can then find many guides to creating RGB color composites in Photoshop, such as this one:
- The FITS Liberator plug-in for Photoshop allows one to read FITS images into Photoshop
- The FITS Liberator User Guide (PDF)
- A step-by-step guide for creating color composite images using Photoshop and FITS Liberator

The end result: a single color composite JPEG image.

rgb_eta_car.jpg

Here are another set of RGB images of an astronomical object -- the Ring Nebula, M51. These images are in the astronomical FITS format, not JPEG, so they may not open in some software packages.