Projection (quick look spectroscopy)
The most interesting overlooked capability is the
projection region. It can be accessed through the
Regions: Shape menu.
It is extremely useful for quick-look spectroscopy.
You can also find out what the size and shape of a region are using
Get Information
Ruler / Distance Measurements
The ruler is another useful tool, particularly during an observing run when you need to find out quickly
how to slew the telescope (e.g. if you're using a coronagraph and the image is at some angle to the plane of the sky)
With the ruler, we can measure positions using get information again.
If your image has WCS coordinates defined, it becomes extremely easy to find out exactly what your slew needs to be.
Multi-Extension FITS
DS9 can also be used to open multi-extension FITS files that IRAF may have trouble with. They will not load
as data cubes by default, though: you must use the
Open Multi-Ext as Data Cube option, or from the command line
use
ds9 -medatacube filename.fits. This is useful for the two-extension data files delivered from
APO's Near Infrared Camera/Fabry Perot Spectrograph
Coordinate Grids
It is possible to make publication-quality images using DS9. Under the
Analysis command menu,
select
Coordinate Grid, then
Coordinate Grid Parameters....
Note that I've used inverted colors so that the image will print nicely on white paper. The format in this
image is, frankly, quite ugly. It is known as
Analysis format. Thankfully, in DS9 5.0, there is a
Type menu that allows you to change to
Publication format. Also, you can change the colors
of each element of the coordinate grid and remove the axes, tickmarks, etc. via the various menus. It will probably
be necessary to modify the locations of the labels as well.
Finally, to save as a postscript,
Print the file to a postscript file instead of saving it.
The resulting
image is mostly satisfactory except
for the annoying presence of the colorbar, which currently cannot be removed except by
editing the postscript directly -
I believe this is a glitch in DS9 that will likely be fixed in the next release.
EDIT 6/23/08: In the latest release(s), you can remove the colorbar using the command line
option
xpaset -p ds9 view colorbar no or by selecting the option in the 'view' menu
Controlling DS9 from the command line
There are some settings you can't change from DS9 directly. For these, you can use
the xpa interface. e.g.
xpaset -p ds9 prefs bgcolor black
xpaset -p ds9 prefs nancolor black
The same can be accomplished by opening DS9 from the command line:
ds9 -prefs nancolor red
