DrizzlePac Notebooks

An updated set of HST drizzling and alignment tutorials are now available and compatible with the latest STScI distributed software environment stenv. These notebooks include a new recommended workflow for MAST data retrieved after December 2019, which includes updated astrometric information included as additional FITS extensions. Alternatively, the new World Coordinate System (WCS) solutions may be downloaded directly from MAST as small ‘headerlet’ files and applied to existing data. For example, the Hubble Advanced Product ‘Single Visit Mosaics’ may have improved relative alignment for different filters acquired in the same visit. These headerlets may be used to update the WCS in the FITS images prior to drizzling. For details on the alignment of HST data in MAST, see Section 4.5 Absolute Astrometry in the DrizzlePac Handbook.

In each notebook, a sample WFC3 or ACS dataset is used to demonstrate how to download the calibrated data, inspect the quality of the alignment, and test whether the observations need to be realigned before combining the data with AstroDrizzle. Different workflows are illustrated to enhance the scientific value of the drizzled data products using advanced reprocessing techniques. These notebooks highlight different use cases, e.g. images acquired using small sub-pixel dithers to optimally sample the PSF versus those acquired in multiple pointings to generate large mosaics on the sky.

The notebooks available in this repository include:

Alignment Workflows:

• Improving Absolute and Relative Astrometry Using Alternate WCS Solutions

• Aligning HST images to an Absolute Reference Catalog

• Aligning Deep Exposures of Sparse Fields

• Aligning Multiple HST Visits

• Using DS9 Regions for Source Inclusion/Exclusion

Drizzling Features:

• Optimizing the Image Sampling for Sub-pixel dithers

• Creating HST mosaics observed with multiple detectors

• Using Sky Matching features for HST mosaics

• Masking satellite trails prior to drizzling

For more information, see the DrizzlePac Handbook and the readthedocs software documentation. For additional assistance with DrizzlePac tools, users may submit a ticket to the STScI Help Desk and should select the DrizzlePac category.

Installation

It is recommended to clone the entire repository. To do so, run the following command in a terminal:

git clone https://github.com/spacetelescope/hst_notebooks

stenv is the preferred base virtual environment for running WFC3 Noteboks since it contains libraries necessary for processing and analyzing data from the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST). To install, see stenv readthedocs or stenv GitHub.

hst_notebooks/notebooks_env is the default virtual environment for HST Notebooks, which contains the same scientific computing libraries in stenv, but not the HST and JWST libraries. This environment can also be used as a base, but is not recommended.

In addition, each notebook contains a requirements.txt file that needs to be installed before running the notebooks. Here is a common set of commands to run before executing the notebooks (assuming your virtual environment is activated):

pip install -r requirements.txt
pip install notebook

With the environment activated and additional libraries installed based on the individual requirement files, you will be able to complete the notebooks.