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pprofile stsdas.hst_calib.ctools



pprofile -- Make radial profile and encircled energy plots.


pprofile input xc yc background target


This task is based on a Fortran program written by Robert Jedrzejewski and includes a subroutine written by Dieter Schertl. The azimuthally averaged profile and the encircled energy are computed with respect to a point in an image. The point may be specified exactly with parameters xc and yc, or those parameters may be taken as initial estimates to be improved by the MPC algorithm as used by the imcntr task. A background value is subtracted from each pixel before the profile and encircled energy are calculated. The profile is normalized by dividing by the center value, and the encircled energy is normalized by dividing by the target value.

The default is to plot both the profile and encircled energy, but either plot or both may be skipped. The X axis is distance in arcseconds. For the profile plot, the Y axis may be either logarithmic or linear. The Y axis will be linear for the encircled-energy plot. After making each plot, the task brings up the interactive cursor. You may continue by hitting return, space bar, or any lower-case key, or you can use the upper-case keys for the standard cursor mode functions, such as "Z" to zoom, "=" to print. The profile is plotted first, and then the encircled energy is plotted. After that the task prompts "change background and replot?" If you respond with "no", the task terminates. If you say "yes", you will be prompted for new values for background and target, and the plots are redrawn.

The profile and encircled energy may also be written to an output text file. One option, therefore, is to write the output to a file and make no plots.

The profile is an array of values at one-pixel increments in radius from the PSF center. The radius is the distance from the star image center to the middle of the one-pixel-wide annulus. The encircled energy includes values out to radius+0.5. Two slightly different algorithms are used to compute the profile. For radii greater than 100 pixels, the full pixel value is added to the profile bin number which is the nearest integer to the radius. For smaller radii, the pixel value is distributed between the two nearest profile bins using the fractional part of the radius as a weight. The profile is then normalized by dividing by the first value in the profile array, which is the value for zero distance from the center.

The radial distance is normally converted from pixels to arcseconds based on the known image scales of the FOC relays. The task determines the relay by getting the value of the OPTCRLY (and possibly also CAMMODE) header keyword. If this keyword is absent or is not "F48" or "F96", or if xunits="pixels", the radial distance is left in units of pixels. This is the only FOC instrument dependence. This task can be used with any 2-D image by setting the values of the parameters xunits and imscale.


input [string]
The name of the input image. This parameter may be the name of a single image, or it may be an "@" sign followed by the name of a text file containing one or more file names (see below), or it may be "STDIN" or "@STDIN". Note that this is not a true file name template.

If only a single image name is given, then the cl parameters xc, yc, background and target are read to get the values for the image specified. If the @filename syntax (or STDIN) is used instead, the values are taken from the input text file. Blank lines and lines beginning with # are ignored. Each line of the file may contain the following five items:

	(1) an image name,
	(2) the X location of the PSF center,
	(3) the Y location of the PSF center,
	(4) the background value to subtract,
	(5) the target value for the encircled energy.
The four numerical values are floating-point numbers, and INDEF is an allowed value. Only the image name is required. If either the background or target is not specified, the value will be taken from the cl parameter with that name. If the center location is not specified, the location of the maximum pixel value in the image is used.

If more than one image is listed in the file, they should all have been taken by the same FOC relay, as specified by the value of the header keyword OPTCRLY. Images which differ from the first in the list in this regard will be skipped.

xc = INDEF [real]
xc and yc are the X and Y coordinates of the center of the PSF, in pixels. If either of these values is INDEF, then the center will be taken as the location of the maximum data value in the image. See also improve_pos.
yc = INDEF [real]
The Y coordinate of the PSF, in pixels.
background = 0. [real]
This value will be subtracted from each pixel of the image.
target = 100. [real, min=1.e-10, max=INDEF]
The encircled energy is normalized by dividing by this value and multiplying by 100 to give percent. To get a curve that reaches 100% at the edge of the PSF, target should be the total number of counts in the PSF. The default gives values of encircled energy in counts, rather than in percent of the total counts in the PSF.

Note that when plotting the encircled energy, if the value of target is too small, the entire curve may be above the range from zero to eymax, in which case the plot will appear blank.

(stddev = no) [boolean]
Should the standard deviations of the profile also be computed and plotted?

These are the standard deviations of the values, not of the mean, and they are normalized the same way the profile is normalized, by dividing by the profile value at the center. The standard deviation at the center pixel may be printed but is not plotted. The standard deviations may be helpful when using this task to determine the background level for a PSF; if the standard deviations increase toward the edge of the image, that implies that the background is not uniform.

(improve_pos = yes) [boolean]
Call the Mountain Photometry Code centering algorithm to refine the xc and xy values?

If there is only one input image, these new xc and yc values will be written back into the parameter file.

(cboxsize = 9) [integer, min=1, max=INDEF]
If improve_pos = yes, then cboxsize gives the size of the square region of the image which is used to find a more accurate position for the PSF.
(rmax = 210) [integer, min=2, max=INDEF]
The profile and encircled energy are computed for radii starting at zero and extending to rmax-1 pixels, or to the edge of the image if that is closer.
(pymax = 1.05) [real]
Upper limit for profile plot. pymax and pymin are the values for a linear Y axis. If logy = yes then the plot limits are taken as the base 10 logarithms of pymax and pymin; however, if pymax is zero or negative, 0.2 is used for the log upper limit, and if pymin is zero or negative, -5 is used for the log lower limit.
(pymin = -0.05) [real]
Lower limit for profile plot.
(eymax = 110.) [real]
Upper limit for the encircled energy plot, in percent. A value of ymax = 110 is reasonable if target is correct. The lower limit for the plot is zero.
(plot_what = "both") [string, allowed values: both | profile |
energy | neither ]

This allows the user to specify that the task should plot both the profile and encircled energy, or either one alone, or neither. If plot_what="neither", then a value should be specified for outfile.

(outfile) [string]
If a value is given for this parameter, then the radius, profile and encircled energy will be written to the file with this name for each input image. The standard deviation of the profile will also be written if stddev=yes. If the file already exists, the current output will be appended.
(xunits = "arcsec") [string, allowed values: pixels | arcsec]

Units used for the X axis. The default is to plot (and print) the X axis values in arcseconds, but setting xunits="pixels" forces the X axis to be in pixels. See also imscale.

(imscale = INDEF) [real]
This parameter is ignored if xunits="pixels". If xunits="arcsec" then imscale is gotten to allow the user to override the scale associated with the FOC focal ratio, or to use this task with non-FOC images. If imscale=INDEF (the default) then the scale for the X-axis is determined from the value of the image header keyword OPTCRLY. (Eventually the task will be changed to get F_RATIO instead.) If OPTCRLY is not present in the header or its value is neither "F48" nor "F96", then the units for the X axis will be pixels. For OPTCRLY = "F48" the scale is 0.04497 arcsec/pixel. For OPTCRLY = "F96" the CAMMODE keyword is gotten to distinguish between f/96 and f/288, for which the scales are 0.02237 and 0.00746 arcsec/pixel respectively. If xunits="arcsec" and imscale is not INDEF then that value (arcseconds/pixel) will be used as the scale for the X axis.
(logy = yes) [boolean]
Should the Y axis be the (base 10) logarithms of the profile?

The encircled energy will be linearly scaled regardless of logy.

(verbose = yes) [boolean]
Print the image name, center position actually used, value of PSF at center, background value, and target?
chg_back = yes [boolean]
Change background and replot?

Whenever the task is run, the user is prompted for this query mode parameter. This gives you the option of changing the background that is subtracted and the target counts for encircled energy and recomputing the profile and encircled energy.

bck [real]
Background value to subtract. This query mode parameter is used to interactively get a new value for the background in the case that chg_back = yes. The user should not set this value using eparam because it will be overwritten by the current value of background.
tgt [real]
This query mode parameter is used to interactively get a new value for the target counts in the case that chg_back = yes. The user should not set this value using eparam because it will be overwritten by the current value of target.
(device = "stdgraph") [string]
The plot device. This may be set to "stdplot" to get hardcopy plots instead of making the plots interactively.


1. Plot the radial profile but not encircled energy of three images. The names and background levels are typed in from the standard input, but the location of the PSF and the target are not specified. The location is therefore determined initially by the maximum pixel and then refined using the imcntr algorithm.

	fo> pprofile STDIN plot_what="profile"
	fo> f430w_a  INDEF  INDEF  0.72		# These four lines
	fo> f430w_b  INDEF  INDEF  1.2		# are typed in
	fo> f430w_c  INDEF  INDEF  2.7		# by the user.
	fo> ^Z					# (That's an EOF.)

2. Print but don't plot the first 10 values of the profile and encircled energy of f430w_a.

	fo> pprofile f430w_a 272 246 0.87 200000 rmax=10 \
	>>>    plot_what="neither" outfile="STDOUT"

3. The text file output from pprofile is shown below for an input image "flat1" filled with the constant value one. The target value was set to 100 so the encircled energy would just be the sum of the counts. A fourth column was added using tcalc with tcalc.equals = "3.141592653589793 * (c1 + 0.5)**2", where "c1" is the value in the first column, i.e., the radius. The third and fourth columns should be equal, so this shows what kind of error can be expected.

	fo> pprofile flat1 23 41 0 100 improve_pos=no xunits=pixels

# flat1, center = [23.000,41.000]
# value = 1., background = 0., target = 100.
#       radius        profile  encircled energy
            0.             1.             1.       0.7854
            1.             1.        7.34315       7.0686
            2.             1.        19.7977      19.6350
            3.             1.        38.8574      38.4845
            4.             1.        63.2675      63.6173
            5.             1.        95.8515      95.0332
            6.             1.        132.851     132.7323
            7.             1.        176.809     176.7146
            8.             1.        227.368     226.9801
            9.             1.        281.678     283.5287
           10.             1.           349.     346.3606
           11.             1.           421.     415.4756
           12.             1.           489.     490.8739
           13.             1.           577.     572.5553
           14.             1.           665.     660.5199
           15.             1.           749.     754.7676


The task prints a peculiar message as it terminates.


This task was written by Phil Hodge based on a Fortran program written by Robert Jedrzejewski.


Type "help focphot opt=sys" for a higher-level description of the focphot package.

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