ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

116 CHAPTER 14. IMAGE ANALYSIS AND DISPLAY
CIA> xphot, raster_pds.raster, psf_dir=’/home/cia/isocia/ia/PSF/’
2. Take a look at Figure 14.1. It contains the image we supplied when invoking xphot, i.e.
a raster MOSAIC, and a number of buttons. The button Select Objects is highlighted, so
the first action you must take is to select the sources that you wish to do photometry on.
Click on Select Objects to begin the selection process. A pop-up window will appear with
some information – read and dismiss. Now you can choose your sources by clicking on
the image. In the example image displayed in Figure 14.1 there is clearly only one source.
Click on done when you are finished making the selection.
3. Now click on Photometric Method to choose the photometric method to apply to the
source. In our example here we will select the first option: simple aperture photometry.
4. The next step is to determine the radius over which to perform the photometry. Click
on Select Radius and choose the simplest method, 1 for all. A new window will appear,
displaying a region of the image centered on the source. Click on this window to indicate
the desired radius. Click done when finished.
5. The final step is to determine the background. Clicking on Select Background will give
you a choice of methods, the simplest being 1 for all. Again, we will choose this option
for our example here. Now select a region of the displayed image for determination of the
background: click on the lower-left point of the region first, followed by the upper-right
point.
6. You can now click on the button compute to perform the photometric calculation according
to the parameters that you have chosen above. The results will be printed to screen in the
following order: the source/object number, its pixel coordinates, the aperture radius, the
background value and the source flux. When you quit xphot (click on quit) these data
will be saved to disk. To recover. . .
CIA> restore,’xphot_tables_final.save’,/verb
% RESTORE: Portable (XDR) SAVE/RESTORE file.
% RESTORE: Save file written by mdelaney@bikini, Thu Oct 9 17:07:40 1997.
% RESTORE: IDL version 5.0 (sunos, sparc).
% RESTORE: Restored variable: ID.
% RESTORE: Restored variable: X.
% RESTORE: Restored variable: Y.
% RESTORE: Restored variable: RAD.
% RESTORE: Restored variable: BKG.
% RESTORE: Restored variable: FLUX.
CIA> print, flux
106.678
14.1.5 Other methods for photometry measurements
This sections describes some other basic tools to perform photometry measurements:
photom psf High level routine to perform PSF photometry. As an example, we restore the
test-dataset, a raster observation of M51 and perform PSF photometry on the companion.
Calling syntax: