6.7 Examples of color plotting
Figure 6.6: KNTR does polarization lines, contours, and grey-scale. Then LWPLA converts the grey-scale to
pseudo-color and colors the lines making dark contours dark but dark polarization lines and stars bright.
Data courtesy of Greg Taylor.
Figure 6.7: KNTR interprets the output of TVHUI as a three-color RGB image and overlays moment-0
contours. LWPLA adds coloring to the lines, using a less than pure white for both bright and dark contours so
that they are not so dominant. Data courtesy of Eric Greisen, Kristine Spekkens, and Gustaaf van Moorsel.
Figure 6.8: PCNTR plots contours and polarization vectors of Centaurus A. Color is used to show the
complex changes in polarization position angle since the angles of short lines cannot be seen accurately.
Data courtesy of Greg Taylor. For a discussion of this amazing pattern see Taylor, G.B., Fabian, A.C.,
& Allen, S.W. 2002, MNRAS, 334, 769, astro-ph/0109337 “Magnetic Fields in the Centaurus Cluster.”
Figure 6.9: PCNTR plots contours every fifth plane from a data cube using colors related to the velocity.
LWPLA adds coloring to the labeling and background and applies a gamma correction to blue. Data courtesy
of Eric Greisen, Kristine Spekkens, and Gustaaf van Moorsel.
Figure 6.10: KNTR plots contours of Cassiopeia A with each contour level separately colored under control
of adverb RGBLEVS. The values of RGBLEVS were set by a procedure call STEPLEVS(10) made available by
RUN SETRGBL. Image is from the Images from the Radio Universe CD, 1992, NRAO with the particular image
from Anderson M., Rudnick, L., Leppik, P, Perley, R. & Braun, R. 1991, ApJ, 373, 146.
Figure 6.11: SNPLT plots phases for four antennas with color indicating polarization and IF channel. Stokes
1, IF BIF is pure red changing through yellow, green, and cyan to Stokes 2, IF EIF as pure blue. When all
symbols lie on top of each other, the last one (pure blue) will dominate.