TVRPLOT: Radial Intensity Plot of an Object on the Image Display

This program makes a simple radial intensity plot of a section of an image. If the object is a star, it shows a mean point-spread function profile. An non-interactive version is available via the RPLOT command.

The radial intensity plot is formed by finding the radius to all points within a given box around the specified location and plotting intensity versus radius. Each point making up the plot is from a single pixel; no interpolation is done. The effect is to produce an azimuthally wrapped (not averaged) plot of intensity. For example, if doing TVRPLOT on the image of a star, if that star is round, then a fairly clean radial point-spread function profile, will be plotted. If the star is elliptical (due to bad guiding or focus), the radial brightness profile will be a fuzzy cloud of points.

The center of the radial plot may be specified in one of two ways:

  1. "C": The center is the intensity centroid nearest the cursor, computed using the same algorithm used by MARKSTAR and AUTOMARK.
  2. "X": The center is the pixel where the display cursor is located. No centroid is computed in this case.
The radius axis on the plot may be scaled to arcseconds using the SCALE= keyword. Note that using SCALE will not affect the size of the search radius; this is always expressed in pixel units.

NOERASE suppresses erasing of the plotting window, allowing you to superimpose subsequent radial plots on top of each other.

LOG will plot the logarithm of the intensity as a function of radius.

COLOR=c changes the color of the points plotted. The default color is white (1). At present only the 7 "primary" graphics colors are available:

Color Codes
Code Color Code Color
0 background 4 Blue
1 foreground 5 Yellow
2 Red 6 Magenta
3 Green 7 Cyan

Colors may be used in conjunction with NOERASE to overlay two different radial profiles, using the colors to distinguish them.

See RPLOT for the non-interactive (batch) version of this program.