pyphot – a photometry tool
This document lays out the basics of installing and using the pyphot script. The image calibration is completed in python and the actual photometry and source detection uses the [sextractor tool].
The latest version of pyspec, along with some example data can be found [here] (2.7MB).
Primarily the instructions are given for Ubuntu, apart from AstroAscii all the required software can be found in the universe repository. Below the Ubuntu instructions are the links to install the software on other distributions. Python (at least Python 2.5.2)
sudo apt-get install python
You may also need to install Ipython: http://ipython.scipy.org/moin/
sudo apt-get install python-pyfits
tar -xvf asciidata-1.1.1.tar
sudo python setup.py install
sudo apt-get install python-scipy
sudo apt-get install sextractor
So you want todo some photometry? Well there is a bit of preparation todo…
Firstly before you run the script you need to ensure that all of your files follow certain conventions:
Bias files should be named bias*.fit where the * represents any postive interger. The same is said for your dark*.fit files. Your target source files should be whatever.FIT – this will be improved in a later version.
You will be asked to input the zero point magnitude ofset and this should be determined by observing a photometric calibrator.
Running the program
Move to the directory you extracted pyphot to and simply type:
Oh, remember to put some data in the directory too! In the zip file is some example data, though this is just some abitary fits files for M31 and the results produced will be non-physical. Outputted data: this includes your soucefilename.FITcal – which is the bias/dark subtracted data. soucefilename.FITcal.cat – is the outputted catalogue from sextractor. cal_output.txt – this is the values of the dark and bias (you can reuse this, the script will ask if you wish to apply the previous calibration)
ALL OF THESE FILES WILL BE OVERWRITTEN BY REPEATING STAGES OF THE TASK – IF YOU WANT TO KEEP THEM COPY THEM TO A DIFFERENT NAME.
That’s it really, its a pretty simple task…