Once
you have DS9 open, go to File>Open and then choose one of the FITS files you downloaded. You
will then see a screen with no obvious
image and mostly black. DS9 is
displaying the full range of pixel values in the image, from 0 to
65,000. In order to make the image more visible, use the Scale
option from the menu bar.
The
scale option in DS9 sets the limits for the image, based on the pixel
values. The example below shows a scale of 99%. The program plots a
histogram of all the pixel values and displays as the image, all
those pixels which are within 99% percent of the mean pixel value. In
this image, 1% of the pixels are thrown away, and these are the black
pixels. This effectively lightens the image so that more detail can
be seen.
Experiment with the different scale functions in DS9 to see
which one shows your image best. Once
you have decided on the best scaling for your image, you can use the Zoom function to zoom in our out of the image, and view the
whole image in the main window.
To
open another image, go to Frame>New Frame to open a new frame in
the same DS9
window.
Then go to File>Open and select the 2nd image. Click on the Zoom
button, then select Zoom to Fit Frame. Select Scale and 99% again. Repeat for any other FITS files you would like to view.
Below is a screencast you can watch that shows the same steps as described above. HD version coming soon!
