|Image Quality of SOFI
2004 - Malvina Billeres
October 2001 - Malvina Billeres
1- The Observations you need
For SOFI you can use the template Image_Quality_SOFI.obx
the link to retreive it if you need).
If you prefer you always can do manually the offset to have the 36
positions on the detector. The main advantage of this method is that
you won't have any problem of elongation due to the telescope motion.
You can pick the offset values in the template above.
You will have 36 positions on the detector (36 fits files).
2- The programs you need
All SOFI scripts and plot programs are ready:
- imagequality.cl : a iraf script to
reduce your data;
- image_quality_3.0.py : a python
script that processes the data;
- plot_mac.f : a fortan program with
smongo inserts to plot the
3- The reduction of the data
The iraf script named
simply substracts the median sky and divides by
flat. (so you need flats !!!). The script needs as input a list of the
raw data (liste*.lis), some flats and it asks to you the prefix you
want to give to the reduced files (ex: LF_J). The final files must be
called LF_J_001.fits to LF_J_036.fits. You have to run it inside iraf,
4- The determination of the image quality
Now you have to use the python program imagequal_3.0.py to extract
the star, calculate the ellipticity and plot some graphs. imagequal_3.0.py needs as input:
example of liste.txt:
First column: directory where the reduced images are
Second column: name of the list of all the fits files
Third column: instrument/configuration : SUSI - EMMI - LARGE - SMALL -
FE _ SO (the last 4 choices are for SOFI)
Fourth column: the prefix for the final files <prefix>
- plot_mac.x: the
executable file of the plot_mac.f program. A
fortran/Smongo program who plots the final results.BE sure that the
plot_mac.x is already compile on the machine you are working on:
problems of uniformity of the machines in La Silla, the librairies are
not updated.......... If the program is not compiled on the machine you
are working, compile it using the command :
f77 -g -o plot_mac.x plot_mac.f
be sure that the path for the
librairies correspond to what you have on your computer.
- The python program reads inside the list file the name of all
the fits files and do an extraction of all the objects in the field
with SEXTRACTOR. The
extraction parameters are in default.sex(they
be modified). For each file, a sex*.cat file is created with all the
positions encountered by SEXTRACTOR (here are the other files needed by
SEXTRACTOR default.conv and default.param).
selects inside each sex*.cat file THE position that
corresponds to the number of the file and the predefined position
(where the star you are looking for should be according to the
template). The numerotation of the files from 001 to 036 is really
important to do the link between the fits file and the position of the
star.A file smongo.dat is created with the
needed parameters for the 36
files : ximage, yimage, A, B, rotational angle.
When the extraction is done, imagequal_3.0.py
the final graph : there are 3 options 1- xterm 2-printer 3-ps file.
It's important to know which option is wanted because the plot cannot
be repeated whitout star again the complete procedure.
At the end you have a <prefix>.dat file and <prefix>.ps
To start the python program, just enter %> python