AstroDrizzle: New software for aligning and combining HST images, with improved handling of astrometric data.
DrizzlePac Software
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
03/29/2013: AstroDrizzle Mini-Workshop CANCELED
01/30/2013: AstroDrizzle Mini-Workshop offered on April 12, 2013
01/29/2013: New headerlet example posted
08/21/2012: AstroDrizzle Error Affecting Saturated Sources in WFC3/IR Images
07/24/2012: Tweakreg and AstroDrizzle video tutorials have been posted.
07/24/2012: An HTML version of the DrizzlePac Handbook has been posted.
07/11/2012: AstroDrizzle replaced MultiDrizzle in the HST pipeline
Introduction
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
There is a wide range of drizzling experience among users who are already familiar with HST data analysis.
- Users new to drizzling should review Chapters 1, 2, and 3 of the DrizzlePac Handbook to become familiar with Drizzle concepts, followed by learning about the DrizzlePac package and how to use it in Chapters 4, 5, and 6. Then, try some examples, starting with Section 7.1.
- Experienced Drizzlers may wish to start with learning about the differences between MultiDrizzle and AstroDrizzle (Chapter 1 and 4), learn about the new Python interfaces in Chapter 5, then come up to speed with DrizzlePac in Chapter 6. The rest of the document could be used as a searchable reference.
Resources
- DrizzlePac Handbook
- Tweakreg and AstroDrizzle Video Tutorials
- Instrument Handbooks
- DrizzlePac Brochure
- Drizzlepac/Astrodrizzle Posters from AAS Meetings
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 |
Some of these examples make use of configuration files (.cfg). A primer on working with configuration files can be found here.
Photometry with DrizzlePac
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
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.