Drizzling ACS images (Circa 2004)
Click here for the January 2009 MultiDrizzle Handbook which supercedes some but not all of this information below.
It should be your starting point for using the current version of MultiDrizzle, including understanding task parameters, current working philosophy behind the various software tasks, and for
examples using the latest methods and versions of the software and its task parameters. The information below, from 2004, may still be applicable in some cases, but is mainly maintained
here at present for historical background and for links to other relevant technical documentation related to the development of the task as it existed in earlier versions. (The original
circa 2004 page complete with its old, original links is below this point, except the link to the PyDrizzle page has been removed since PyDrizzle documentation is now incorporated into the MultiDrizzle
Handbook.)
See the
ACS dither
web page for information on designing and using ACS pointing patterns.
The following list of documents provide information about reducing
dithered or mosaiced data:
- How such data are handled by the CALACS
calibration pipeline, including the drizzling of
associated datasets by PyDrizzle
- The use of MultiDrizzle
(Koekemoer et al. 2002, HST Calibration Workshop, p. 337) to associate data,
refine shift measurements, and reject cosmic rays.
- Reproduceable examples which illustrate the
use of all of the above
Drizzling mechanics
MultiDrizzle implementation in the ACS pipeline
As of September 22, 2004, MultiDrizzle has been incorporated into the ACS data
reduction pipeline. This page describes
some details of the implementation and resulting image products.
The ACS Data Handbook
Mack et al., 2003,
Chapter 3
describes pipeline processing, including PyDrizzle;
Chapter 4
provides detailed drizzling guidance, including the rejection of
cosmic rays and image registration with MultiDrizzle
The MultiDrizzle webpage
Hack & Jedrzejewski, 2002, MultiDrizzle is currently a stand alone
IRAF/STSDAS task which must be downloaded and installed;
requires PyRAF; does not yet include automated shift tweaking
Reduction of the Helix Nebula mosaic
Mutchler, 2003, a detailed example of drizzling a large ACS mosaic
(the F656N WFC mosaic is displayed above), which can be
reproduced with
FITS data
also provided
Drizzling reference
Andy Fruchter's dithering webpage
Fruchter, 1996
Drizzle: A Method for the Linear Reconstruction of Undersampled Images
Fruchter & Hook, PASP, 114: 144-152, 2002 February
Anton Koekemoer's MultiDrizzle webpage
Koekemoer, 2002
(describes use of the full-featured
version with shift tweaking)
MultiDrizzle: An Integrated Pyraf Script for Registering, Cleaning and Combining
Images (PDF)
Koekemoer, Fruchter, Hook, Hack, 2002,
HST Calibration Workshop Proceedings
(details about Multidrizzle steps and parameter settings)
HRC mosaic simulation (PDF)
Mutchler, 2001, previous version of this webpage;
pre-flight testing of drizzle software with simulated data
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