Chandra observers making 3-color images should be interested in the preprint
referenced below. Lupton et al. describe how many of us could and should be
making 3-color images that are better representations of the data.
In a blatant act of self promotion I'll mention here that the interactive tool
"true_color_image" in the most recent release of my TARA package implements a
color-preserving scaling similar to that described by Lupton et al. We don't
yet have the asinh stretch Lupton uses, and true_color_image is not nearly as
polished as the gold standard ds9, but the tool is available and might be
helpful to you. See
http://www.astro.psu.edu/xray/docs/TARA/TARA_users_guide/node8.html for a brief
description, and http://www.astro.psu.edu/xray/docs/TARA/index.html for the IDL
code. You're welcome to contact me for questions/problems/suggestions.
Patrick Broos
Paper: astro-ph/0312483
From: Robert Lupton <rhl@astro.princeton.edu>
Date: Thu, 18 Dec 2003 13:56:09 GMT (1735kb)
Title: Preparing Red-Green-Blue (RGB) Images from CCD Data
Authors: Robert Lupton, Michael R. Blanton, George Fekete, David W. Hogg, Wil
O'Mullane, Alex Szalay, N. Wherry
We present a new, and we believe arguably correct, algorithm for producing
Red-Green-Blue (RBG) composites from 3-band astronomical images. Our method
ensures that an object with a specified astronomical color (e.g. g-r and r-i)
has a unique color in the RGB image, as opposed to the burnt-out white stars to
which we are accustomed. A natural consequence of this is that we can use the
same colors to code color-magnitude diagrams, providing a natural `index' to
our images. We also introduce the use of an asinh stretch, which allows us to
show faint objects while simultaneously preserving the structure of brighter
objects in the field, such as the spiral arms of large galaxies. We believe
that, in addition to their aesthetic value, our images convey far more
information than do the traditional ones, and provide examples from Sloan
Digital Sky Survey (SDSS) imaging, the Hubble Deep Field (HDF), and Chandra to
support our claims. More examples are available at
http://www.astro.princeton.edu/~rhl/PrettyPictures
http://arXiv.org/abs/astro-ph/0312483
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