Introduction

Welcome to the AstroData User’s Manual, a user guide for the astrodata package. astrodata was formerly a part of the DRAGONS data reduction suite developed at the Gemini Observatory. It has undergone several iteractions of major development and improvements, and is now designed as a standalone solution for handling astronomical data.

astrodata consolidates the handling of astronomical data into a single package, using a uniform interface to access and manipulate data from different instruments and observing modes. It is designed to be used in conjunction with Astropy, Numpy and other scientific Python packages.

This introduction will guide you through the installation process and provide a brief overview of the package. If you are looking for a quick reference, please head to the Cheat Sheet.

What is `astrodata`?

astrodata is a package that wraps together tools to represent internally astronomical datasets stored on disks and to properly parse their metadata using the AstroData and the TagSet classes. astrodata provides uniform interfaces for working on datasets from different instruments. Once a dataset has been opened with from_file(), the object assesses metadata to determine the appropriate class and methods to use for reading and processing the data. Information like instrument, observation mode, and how to access headers, is readily available through the AstroData uniform interface returned by from_file(). All the details are coded inside the class associated with the instrument, that class then provides the interface. The appropriate class is selected automatically when the file is opened and inspected by astrodata.

Currently astrodata implements a basic representation for Multi-Extension FITS (MEF) files. Extending to other file formats is possible, but requires programming (see the Developer Guide for more information).

Installing Astrodata

Using pip

The astrodata package has a number of dependencies. These can be found in the requirements.txt file in the source code repository.

To install the standalone astrodata package, you can use pip:

$ pip install astrodata

Or you can install it from the source code:

git clone https://github.com/GeminiDRSoftware/astrodata
cd astrodata # Or the directory where you cloned the repository
pip install -e .

If you’re interested in using astrodata out-of-the-box with a specific type of data, you may want to install the astrodata package together with their extensions. astrodata alone defines a base class, AstroData, which is meant to be extended with instrument-specific classes. For example, to use astrodata with Gemini data, you will need to install DRAGONS, which includes the astrodata package and its extensions for DRAGONS:gemini_instruments.

Source code

The source code is available on Github:

https://github.com/GeminiDRSoftware/DRAGONS

A quick example

Here is a quick example of how to use astrodata to open a file and access its metadata using an AstroData object

import astrodata

# Create a fake file to use.
from astrodata.testing import create_test_file

# We can create a fake file to use for this example:
path = create_test_file(include_header_keys=['INSTRUME', 'EXPTIME', 'DATE-OBS'])
ad = astrodata.from_file(path)
print(ad.phu['INSTRUME'])

'TEST_VALUE'

All file opening, closing and metadata management (which selects the appropriate class for the header data) are handled by astrodata. There is no need to “close” the ad object, as all file handles are closed when no longer required or the program finishes.

Astrodata Support

Astrodata is developed and supported by staff at the Gemini Observatory. Questions about the reduction of Gemini data should be directed to the Gemini Helpdesk system at https://noirlab.atlassian.net/servicedesk/customer/portal/12.

Issues related to astrodata itself can be reported at our github Issue Tracker.