1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
|
.help kpnofocus Mar96 noao.obsutil
.ih
NAME
kpnofocus -- Determine the best focus from KPNO focus images
.ih
USAGE
kpnofocus images
.ih
PARAMETERS
.ls images
List of focus images.
.le
.ls frame = 1
The image display is checked to see if the image is already in one of
the display frames. If it is not the \fBdisplay\fR task is called to
display the image in the frame specified by the \fBframe\fR parameter. All
other display parameters are taken from the current settings of the task.
This option requires that the image display be active.
.le
.ls level = 0.5
The parameter used to quantify an object image size is the radius from the
image center enclosing the fraction of the total flux given by this
parameter. If the value is greater than 1 it is treated as a percentage.
.le
.ls size = "FWHM" (Radius|FWHM|GFWHM|MFWHM)
There are four ways the PSF size may be shown in graphs and given in
the output. These are:
.nf
Radius - the radius enclosing the specified fraction of the flux
FWHM - a direct FWHM from the measured radial profile
GFWHM - the FWHM of the best fit Gaussian profile
MFWHM - the FWHM of the best fit Moffat profile
.fi
The labels in the graphs and output will be the value of this parameter
to distinguish the different types of size measurements.
.le
.ls beta = INDEF
For the Moffat profile fit (size = MFWHM) the exponent parameter may
be fixed at a specified value or left free to be determined from the
fit. The exponent parameter is determined by the fit if \fIbeta\fR
task parameter is INDEF.
.le
.ls scale = 1.
Pixel scale in user units per pixel. Usually the value is 1 to measure
sizes in pixels or the image pixel scale in arc seconds per pixel.
.le
.ls radius = 5., iterations = 2
Measurement radius in pixels and number of iterations on the radius. The
enclosed flux profile is measured out to this radius. This radius may be
adjusted if the \fIiteration\fR parameter is greater than 1. In that case
after each iteration a new radius is computed from the previous FWHM
estimate to be the radius the equivalent gaussian enclosing 99.5% of the
light. The purpose of this is so that if the initial PSF size of the image
need not be known. However, the radius should then be larger than true
image size since the iterations best converge to smaller values.
.le
.ls sbuffer = 5., swidth = 5.
Sky buffer and sky width in pixels. The buffer is added to the specified
measurement \fIradius\fR to define the inner radius for a circular sky
aperture. The sky width is the width of the circular sky aperture.
.le
.ls saturation=INDEF, ignore_sat=no
Data values (prior to sky subtraction) to be considered saturated within
measurement radius. A value of INDEF treats all pixels as unsaturated. If
a measurement has saturated pixels there are two actions. If
\fIignore_sat\fR=no then a warning is given but the measurement is saved
for use. The object will also be indicated as saturated in the output
log. If \fIignore_sat\fR=yes then a warning is given and the object is
discarded as if it was not measured. In a focus sequence only the
saturated objects are discarded and not the whole sequence.
.le
.ls logfile = "logfile"
File in which to record the final results. If no log file is desired a
null string may be specified.
.le
.ih
CURSOR COMMANDS
When selecting objects with the image cursor the following commands are
available.
.nf
? Page cursor command summary
g Measure object and graph the results.
m Measure object.
q Quit object marking and go to next image.
At the end of all images go to analysis of all measurements.
:show Show current results.
.fi
When in the interactive graphics the following cursor commands are available.
All plots may not be available depending on the number of focus values and
the number of stars.
.nf
? Page cursor command summary
a Spatial plot at a single focus
b Spatial plot of best focus values
d Delete star nearest to cursor
e Enclosed flux for stars at one focus and one star at all focus
f Size and ellipticity vs focus for all data
i Information about point nearest the cursor
m Size and ellipticity vs relative magnitude at one focus
n Normalize enclosed flux at x cursor position
o Offset enclosed flux to by adjusting background
p Radial profiles for stars at one focus and one star at all focus
q Quit
r Redraw
s Toggle magnitude symbols in spatial plots
t Size and ellipticity vs radius from field center at one focus
u Undelete all deleted points
x Delete nearest point, star, or focus (selected by query)
z Zoom to a single measurement
<space> Step through different focus or stars in current plot type
:beta <val> Beta parameter for Moffat fits
:level <val> Level at which the size parameter is evaluated
:overplot <y|n> Overplot the profiles from the narrowest profile?
:radius <val> Change profile radius
:show <file> Page all information for the current set of objects
:size <type> Size type (Radius|FWHM)
:scale <val> Pixel scale for size values
:xcenter <val> X field center for radius from field center plots
:ycenter <val> Y field center for radius from field center plots
The profile radius may not exceed the initial value set by the task
parameter.
.fi
.ih
DESCRIPTION
This task is a script based on the task \fBstarfocus\fR. The details
of the algorithms and display modes are given in the help for that
task. The purpose of \fBkpnofocus\fR is to provide a simpler task
with fewer parameters because the format of the multiple exposure
images is given by header keywords.
As a summary of the algorithm, the center of each star image is
found using centroids, a background is determined from the mode
of a sky annulus, and the enclosed flux profile is measured. The
PSF width is then the radius enclose a specified fraction of the
flux. Alternatively a direct FWHM from the radial intensity profile,
a FWHM for a Moffat profile fit to the enclosed flux profile, or
a FWHM for a Gaussian profile fit to the enclosed flux profile may be
used.
If a saturation value is specified then all pixels within the specified
measurement radius are checked for saturation. If any saturated pixels are
found a warning is given and \fIignore_sat\fR parameter may be used ot
ignore the measurement. If not ignored the object will still be indicated
as saturated in the output log. In a focus sequence only the saturated
objects are discarded and not the whole sequence.
To use this task consists of specifying a focus image name. Multiple
images could be analyzed together but this is uncommon. The task
will then display the image, using the current parameters of the
\fBdisplay\fR task, if the image is not already in the display.
The user then marks the first exposure (the top one) by pointing
the image cursor and typing 'm'. This may be done for more than
one star if desired. After all stars to be used are marked type
'q' to go to the graphical analysis.
A plot showing the variation of the PSF width and ellipticity with
focus is shown along with a magnitude weighted, parabolic
interpolated estimate for the best focus. One may delete bad points
with the cursor 'd' key. To exit and record the results to
a logfile use the 'q' key. There are many graphical display
options for more sophisticated analysis such as variations with
position. The best thing to do is to try the various keystroke
commands given in the CURSOR section. For details about
the various plots see the \fBstarfocus\fR help.
The other task parameters allow setting the enclosed flux level,
the object and sky apertures, and the type and scale of the
reported PSF size. The log filename may also be specified.
.ih
EXAMPLES
1. A multiple exposure frame is taken with 7 exposures of a bright
star, each exposure shifted by 30 pixels using the version of the
ICE software which records the focus information in the keywords
FOCSTART, FOCSTEP, FOCNEXPO, and FOCSHIFT.
.nf
cl> kpnofocus focus1
<The image is displayed and the image cursor activated>
<The bright star is marked with 'm'>
<Marking is finished with 'q'>
<A graph of FWHM vs focus is shown>
<Exit with 'q'>
NOAO/IRAF IRAFV2.10.3 valdes@puppis Fri 15:48:01 12-Nov-93
Image Column Line Mag Focus FWHM Ellip PA SAT
36inch1 536.63 804.03 0.07 4660. 13.878 0.06 -11
535.94 753.28 -0.12 4680. 8.569 0.09 89
535.38 703.96 -0.08 4700. 5.164 0.11 -88
537.12 655.36 -0.02 4720. 3.050 0.08 -77
534.20 604.59 0.00 4740. 4.336 0.11 74
534.41 554.99 -0.00 4760. 9.769 0.09 -35
534.83 456.08 0.16 4780. 12.569 0.13 -10
Best focus of 4722.44 with FWHM (at 50% level) of 3.02
.fi
The estimated best focus is between the 4th and 5th focus setting
at a value of 4722.4 and the best focus FWHM is 3.02 pixels.
.ih
SEE ALSO
.nf
imexamine, implot, pprofile, pradprof, psfmeasure, radlist,
radplt, radprof, ranges, specfocus, splot, starfocus
.endhelp
|
