Hot pixels are easily seen in dark frames as pixels with unusually high signal over the
background. The following lines describe a way of measuring the total number and distribution
of these pixels between the different quadrants.
The number of hot pixels seem to depend on integration time and array temperature. Therefore,
it is suggested to monitor the number of hot pixels using fixed integration times (e.g. 10s)
and keeping record of the temperature of the array.
Take a dark frame of 10s:
Put blanks into the INGRID light path: SYS>filter ingrid blank
Set the number of coaverages and the mndr to 1: SYS>rmode ingrid mndr 1 1
Take a dark frame: SYS>dark ingrid 10 "dark 10s"
Write down the run number containing your dark frame (rxxxxxx.fit).
Get the post - pre of the dark frame
Copy the file in your working directory:
e.g. cp /obsdata/whte/rxxxxxx.fit /scratch/whta/my_directory
Open an IRAF session (open an xgterm and then type ncl or cl)
Change to the directory where you have the dark frame cl> cd /scratch/whta/my_directory
Start the INGRID quick look package: cl>ingrid_ql
Type: in>iframediff rxxxxxx.fit rxxxxxxpp.fits
rxxxxxxpp.fits contains the post-pre file.
Measure the number of hot pixels
Copy the file hot.pix.pro into your working directory.
Edit the file (e.g. type emacs hot.pix.pro&)
and change the 'darkfile' input parameter
(darkfile='rxxxxxxpp.fits') and save the changes.
Open an IDL session (on a terminal or xgterm type idl)
Type: IDL>.run hot.pix.pro
The program will take about 60 seconds to finish. Afterwards you will get an
output like this, with info about
the total number of hot pixels in the array and per quadrants.
Do not forget to exit the IDL session, there are only a few licenses available!
(Type: IDL>exit)