Observational tools for handling FITS files.

Primarily, this tool provides a command PO which can be used to examine FITS file headers and manipulate starlists.

To install this module, use the python installation command pip:

$ pip install .

Installing the module with pip install -e . installs it so that you can make changes to the source files and have those changes automatically take effect. pip will ensure that your computer has all of the required dependencies.

To get help information, use PO -h. PO has several commands for working with FITS files, and one command for working with Starlists/ds9 regions.

• PO list: Create a list of files. Optionally, search through their headers, and only list ones matching specific criteria.
• PO log: Create a log of files with specific header keywords included. Optionally, search.
• PO group: Group a collection of files based on keyword values. This quickly tells you how many files have identical values for a set of keywords.
• PO info: Show the HDU information for a bunch of FITS files. This shows extension HDUs, HDU types and sizes.
• PO inspect: Similar to PO list, but pulls each image up in ds9, and asks the user whether they want to keep that image or not.

Most PO commands can search through your FITS files using header keywords. When supplying the keywords to the PO command, you can use a KEYWORD=value syntax. The value will be interpreted as a python literal, or as a string (so you don't need to put quotes around strings that don't have spaces). This means that entering OBJECT=galaxy will search for files with the header keyword OBJECT set to the value "galaxy". This works for other python literals (int, float etc.) which might appear in header keywords.

The --re option for all search commands changes the value to a regular expression. Therefore --re OBJECT=gal(axy)? will find header keywords which match either gal or galaxy or contain either of those strings. (This is a dumb example. There are lots of good tutorials on regular expressions online. The python re documentation is a decent place to start.).

• PO slds9: Convert between starlists and ds9 region files.