Image-Processing Techniques for the Creation of Presentation-Quality Astronomical Images

Abstract

The quality of modern astronomical data, the power of modern computers and the agility of current image-processing software enable the creation of highquality images in a purely digital form. The combination of these technological advancements has created a new ability to make color astronomical images. And in many ways it has led to a new philosophy towards how to create them. A practical guide is presented on how to generate astronomical images from research data with powerful image-processing programs. These programs use a layering metaphor that allows for an unlimited number of astronomical datasets to be combined in any desired color scheme, creating an immense parameter space to be explored using an iterative approach. Several examples of image creation are presented.A philosophy is also presented on how to use color and composition to create images that simultaneously highlight scientific detail and are aesthetically

Gass: The Parkes Galactic All-Sky Survey. I. Survey Description, Goals, and Initial Data Release

“…The intensity of each color corresponds to the brightness temperature integrated over the ∼40 km s −1 velocity chunk, and is scaled logarithmically as shown by the horizontal extent of the color bar. Where emission exists at two different velocities, the intensities are combined using the "screen" algorithm in GIMP as described by Rector et al (2007). Some artifacts from scanning were masked by hand.…”

“…Some artifacts from scanning were masked by hand. This image was made following the procedure detailed by Rector et al (2007). Figure 13 as GP (top), GP2 (middle), and LMC (bottom).…”

The Aesthetics of Astrophysics: How to Make Appealing Color-composite Images that Convey the Science

“…Data from multiple instruments and/or telescopes should be projected to a common world coordinate system (WCS). Rector et al (2007) offer a detailed explanation for the steps necessary to create a high-quality color-composite image from this data. In brief, the process can be distilled into the following steps: (1) convert (or "project") each dataset into a grayscale image; (2) import these images as layers into an IP software package; (3) adjust the intensity scaling of each layer to better show detail (i.e., increase contrast in regions of interest); (4) assign a color to each layer; (5) fine tune the image, which includes overall color balance, the removal of residual artifacts, and orientation and framing; and (6) prepare the image for electronic distribution and print production.…”

“…For this reason, many journals have guidelines as to what image modifications are acceptable, e.g., Nature (2006). Rector et al (2007) explain how different color schemes can be used when creating an image, with examples. Several terms have come into usage to describe these color schemes.…”

“…As with cosmetic retouching and other image manipulations, cropping and rotation should not be used to misrepresent; e.g., selectively cropping a field to remove objects that run counter to the scientific narrative. For this reason it is recommended (Rector et al 2006) was rotated and cropped in accordance to the rule of thirds (as shown by the red grid overlaid onto the right image). Structure in the nebula naturally produces several "lines."…”