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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<head>
<title>Image probe </title>
</head>
<body>
<h1>Image Probe </h1>
<h2>Overview</h2>
Given a probe, this tool calculates the its centroid coordinates
and region statistics such as total number of pixels,
total sum of the pixel values (flux) and mean pixel value (mean flux).
When the image probe dialog box is open, POW is in the "probe" mode.
To go back to the normal mode, user can just simply press the
<B>Exit</B> button and return to the normal mode.
<h2>Creating and manipulating probe</h2>
<p>A probe basically is a region. Its shape can be selected by
clicking the <B>Probe Shape </B> button. The available shapes
are Circle, Box, Ellipse, and Polygon. To create a new probe,
place the mouse at the desired location in the graph and
click-and-drag with the right mouse button down (Command-Click on
Mac-OS). For Circle and Ellipses, the initial mouse location is
the center of the probe and the final location is its radius or
width and/or height. For Boxes, the mouse movements traces out
opposite corner of the rectangle. For Polygon, the mouse locations
determines its verteces. To add extra segments to the Polygon,
let up on the mouse button, press it again without moving, and
drag it to the next vertex. </p>
<p> To move a probe, simply put cursor inside the probe, and click-and-
drag it to the new position with the left mouse. The left mouse is
also used for changing and rotating probe. To change the shape, click-
and-drag the "change" handle (a small green box) on the probe.
To rotate the probe, click-and-drag the "rotation" handle (a small
green triangle). The rotation only applies to the shape of ellipse
and box. </p>
<p>For details of creating and manipulating the probe, please refer
to the Regions help file. </p>
<h2>Calculating the coordinates of centroid and statistics </h2>
<p>Whenever the probe is created, changed, moved or rotated, the
coordinates of centroid and statistics are calculated and
shown in the Image Probe dialog box. </p>
<p>The coordinates of centroid are presented in two ways, in
pixel in the <B> Pixel </B> field, and in the graphical coordinate
in the <B> Coordinate </B> field. The format of graphical coordinate
is either in decimal or hms, determined by the <B> Coord. Format </B>
button. </p>
<p>The statistics of a probe includes total number of pixels ( the <B> N
Pixels </B> field), total flux (the <B> Total Flux </B> field) and mean
flux (the <B> Mean Flux </B> field). The mean flux is defined as the
average flux per pixel inside the probe. </p>
<h2>Saving the coordinates of centroid and statistics </h2>
<p>To save the coordinates of centroid and statistics of current probe
to a disk log file, click the <B> Record </B> button. For the first recording
or after closing the current log file, you have chance to enter the log
file name through a opened file dialog box. To close the current log
file, press the <B> Close Log </B> button.</p>
</body>
</html>
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