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Hubble Space Telescope
DrizzlePac

AstroDrizzle: New Software for Aligning and Combining
HST Images, With Improved Handling of Astrometric Data

DrizzlePac Software

DrizzlePac Release Notes

Latest Public Release
Available as part of stsci_python

Latest Development Version
Available via IRAFX (updated regularly). For the latest version, see the DrizzlePac release notes.

Drizzlepac News

News Archive

Introduction

Introduction Page

DrizzlePac in a nutshell:

  • AstroDrizzle replaces MultiDrizzle.
  • All astrometric and distortion information will be included in calibrated images, removing the need for external calibration files.
  • Multiple astrometric solutions that are tied to another image, a standard catalog, or user-created catalog, can be generated and stored in the image header under unique labels.
  • Astrometric solutions can be exchanged among users in the form of small FITS files called ‘headerlets.’
  • Task parameter settings can be easily saved to ‘configuration files’ for future use or to share with collaborators.
  • Parallelization will speed up processing of images.

Using AstroDrizzle to Improve the Resolution of Hubble Images

Getting Started

Getting Started Page

There is a wide range of drizzling experience among users who are already familiar with HST data analysis.

Resources

Examples

Title Goal Data Description DrizzlePac Tasks
WFC3/UVIS: Optimizing Image Alignment for Multiple Visits Align and combine three images taken at different visits and orientations. Three full-frame UVIS F606W images of Omega Centauri, each with exposure time of 40 sec., each taken in a different visit with different roll angle and offset. Tweakreg AstroDrizzle
WFC3/IR: Optimizing Image Sampling for a Single Visit Optimize image sampling using final_pixfrac and final_scale settings in astrodrizzle, for WFC3/IR images. Spiral galaxy NGC 3370 in F160W, observed with a WFC3-IR-DITHERBOX-MIN pattern. All observations in the same visit with same orientation. AstroDrizzle
ACS/WFC: Optimizing Image Alignment for Multiple Visits Align and combine three images taken at different visits and orientations. Three F606W images of the dense star field NGC 104, each with exposure time 339 sec.. The images are CTE-corrected flat field-calibrated files with suffix flc.fits. Tweakreg AstroDrizzle
ACS/WFC: Optimizing Image Sampling for a Single Visit Optimize image sampling using final_pixfrac and final_scale settings in astrodrizzle, for ACS/WFC images. A two-point dither line with subpixel dithers at each point: four images of galaxy NGC 4449 taken with the F555W filter. The images are CTE-corrected flat field-calibrated files with suffix flc.fits. AstroDrizzle
WFC3/UVIS: Aligning Images in Different Filters by Defining an Output Reference Frame Two sets of drizzled images, each for a different filter, are aligned by WCS and in pixel space. Observations of galaxy M83 in F814W and F438W, each filter set taken in different visits. There are three images per filter. Tweakback Tweakreg AstroDrizzle
WFC3/UVIS: Alignment of Sparse Fields Using Headerlets Use headerlets to align and combine three images with a high degree of precision. Three full-frame 420-second UVIS F606W images of GRB-110328A observed in a 3-point dither pattern. Tweakreg AstroDrizzle Apply_headerlet
WFPC2: Aligning and Drizzling WFPC2 Images Strategies for dealing with severely undersampled WFPC2 images. Six dithered images of Messier 2. Most objects are in the WF chips (plate scale 0.1"/pixel). Tweakreg AstroDrizzle apply_headerlet_as_primary
SExtractor Catalogs to Align ACS/WFC Images Using External SExtractor (v2.8.6) Catalogs from *_crclean.fits Images to Align ACS/WFC Images With Drizzlepac/Tweakreg Alignment of four ACS/WFC images, about 60 pixels apart, using a catalog generated by SExtractor. The image contains a large number of extended sources, but relatively few point sources TweakReg TweakBack AstroDrizzle SExtractor

Some of these examples make use of configuration files (.cfg). A primer on working with configuration files can be found here.

Photometry with DrizzlePac

Photometry
Demo Page

The goal of this demonstration is to assert the accuracy of aperture photometry measurements on ACS/WFC images using the new software package Drizzlepac. With this goal in mind, we compare stellar instrumental magnitudes calculated using individual FLT images from the HST pipeline with the instrumental magnitudes of the same sources estimated using the AstroDrizzle output.

Frequently Asked Questions

FAQ Page

Based on the input of users here at STScI and that of users in the broader astronomical community, we have compiled a list of frequently asked questions that we feel addresses some of the issues most commonly encountered by DrizzlePac and AstroDrizzle users.

If you cannot find a solution to your particular problem in either the FAQ page or in any of the five examples above, please contact help@stsci.edu.