Image Display Software
The image display software for ShARCS is run on the computer covert with the command sharcsdisplay. This command will bring up a number of windows: Image Browser, sharcsdisp, Radial Profile, FocFit, and an xterminal for display text information and IDL output.
The sharcsdisp window (Figure 1) is the primary image display GUI for
the ShARCS camera. Images are automatically displayed after they are
written to disk. The compass rose will indicate which direction is
North and the axes are in arcsecond units by default. As the cursor
is moved around the image, the pixel positon and value will be
displayed below the image as well as the minimum and maximum pixel
values in the data. Above the image is displayed the file name and
object name from the FITS header. When using the FWHM tool in the Image Browser, an estimate of Strehl for the
selected object will be displayed above the image as well.
The radio buttons at the bottom of the sharcsdisp window allow one to
choose what action is taken when clicking on a spot in the image.
Zoom will zoom in on the clicked position, which Unzoom
will do the opposite. Recenter allows one to pan the image,
recentering the zoomed image on the pixel clicked. The
FullImage button will resize the image to fit in the display
window.
The File menu (Figure 2) has two items Show Header and
ReadFits. Show Header will bring up a GUI showing the text of
the FITS header for the currently displayed image. ReadFits brings up
a dialog GUI to select a FITS file in /data/sharcs/ to display.
The color map used to display the images can be changed using the
ColorMap menu (Figure 3). The last item in the menu,
XLoadCT, allows one to load any of the IDL color maps if none
of the pre-selected color maps is desired.
The Axes menu (Figure 4) selects which axes and units to
overlay on the image display. No Axes will overlay no axes on
the image. Sky Arcseconds, the default, displays the X and Y
axes in arcsecond units. Sky Pixels will display the axes in
pixel units, with the lower left corner of the image display as
coordinate (0,0). Note that the Real Detector Pixel X and Y
coordinates are also displayed on the upper and right borders of the
image. Detector Pixels displays the detector pixels values
(which are rotated and flipped from the sky pixel coordinate system).
If one wants to window the chip to read out only a sub-region, the Window GUI in sharcs_fe uses the
detector pixel values for defining the region. A compass rose may
also be overlaid on the image, indicating north and east by clicking
on Show compass and hiden from view by selecting Hide
compass. The orientation is read from the instrument position
angle in the FITS header keyword TUBANGLE.
The Image Browser GUI (Figure 5)is the main window for image display
manipulation. Labeled buttons perform that function when pressed. The
radio buttons to the left of the labeled buttons determine which
functions are automatically done when a new image is displayed. Radio
buttons that are on are depressed and red in color.
The newest button at the top of the window will display the most
recent ShARCS image. In the parentheses will be the most recent image
number or unknown if no image has been taken since sharcsdisplay was
started.
The Display Image # button allows you display the image of your
choice. Enter the desired image number in the box to the right. You
may also increment or decrement the image number to be displayed by
using the up and down arrows on the right.
The Subtract Image # button enables the subtraction of an image
from the displayed image. Enter the desired image number to be
subtracted in the box to the right. You may also increment or
decrement the image number to be subtracted by using the up and down
arrows on the right.
The full range button displays the current image over the
entire range of pixel values, scaling the color map accordingly.
The sigdisp button displays the current image over a range of
pixel values x sigma around the mean. Default is 12 sigma, but can be
changed in the box to the right. Commonly used values are 1, 3, and 5
sigma in addition to the default.
The minmax button displays the current image over the range of
pixels values specified in the boxes to the right.
The log button displays the current image logarithmically
scaled over the range of pixel values specified in the boxes to the
right.
The stats button displays the mean and standard deviation of
the image pixel values.
The fwhm button calculates the FWHM, centroid, and estimates
the Strehl of a source in the image. The measurements are displayed in
the xterm window from which sharcdisplay was started in following
format (for example):
The badpix button will remove the badpixels in the image (based
on an existing bad pixel mask), replacing them with the median of the
surrounding pixels. This is somewhat time consuming, but can be
useful particularly when imaging faint objects.
The Move Tel button allows you to move the telescope by
clicking on the image. This is particularly useful for positioning an
object on a particular pixel in the array. Click on Move Tel, then
click on the object, then click the position you wish to object to
be. The telescope and optics in the ShaneAO system should move the
proper distance and direction to put the target on the desired
position on the chip.
The two IDL buttons allow IDL commands to be executed. Enter the
command in the dialog box and press the IDL button to send it. The
currently displayed image is called img in the IDL session and you can
manipulate the image using regular IDL commands.
The reset IDL button sends an IDL retall command in case the
Image Browser gives an IDL error or gets confused on which display
window is which, or fails to display the new image. This is a good
general fix to most problems that the Image Browser occasionally
exhibits.
The hardcopy button sends the currently displayed image in the
sharcsdisplay window to the printer in the 3-m control room (note,
this is not currently functioning).
The focfit, focval, and focfit init are used for
ShARCS image sharpening and not generally used by the observer. The
focfit program fits a parabola to the Strehl of each image at various
focus or other aberration mode values and prints the best focus
value. In addition, focfit displays a zoomed view of the image around
the point source being measured. The focval entry box is the focus (or
image sharpening mode) value. The focfit init button initializes the
focus fitting program using the focval entry and Strehl of the current
image as the first data point. The focfit button adds new data points
(Strehl and focval entry) to the parabola fitting program. The
following procedure is typically used for focusing ShARCS with focfit:
The Config menu has two selections: Configure and Update
newest file. Update newest file
simply looks in the current data directory for the most recent file
and displays it. Configure brings up a window where you can change the
data path, the FWHM and photometry radii parameters for the
FWHM/Strehl estimating routine, and if the new image always zooms to
fill the display window.
sharcsdisp
Figure 1: Image Display GUI, sharcsdisp.
Figure 2: File Menu
Figure 3: ColorMap Menu
Figure 4: Axes Menu
Image Browser
xcen ycen peak( g / r ) (x / y)fwhm npfwhm (x / y)fwhm" npfwhm"
47.5 55.6 10967. / 11215. 3.29 / 3.26 3.53 0.11 / 0.11 0.12
flux sky strehl / congridstrehl
227161. -14.0 0.30 / 0.30
The x and y centroid from a gaussian fit of the object are xcen and ycen.
The peak flux of the source is calculated two ways: the peak of the
gaussian fit (g) and the measured peak of the object (r).
xfwhm and yfwhm are the x and y FWHM calculated from the gaussian fit to
the object in pixels.
xfwhm" and yfwhm" are the x and y FWHM calculated from the gaussian
fit to the object in arcseconds.
npfwhm is the FWHM in arcseconds calculated directly from the number
of pixels above half the peak value.
The total flux of the star is total (sky subtracted) counts inside the
photometry aperture.
The sky flux displayed is the average per pixel as measured in the sky
aperture.
The estimated Strehl is calculated twice, based on the peak
measurements from the data and the gaussian fit:
Strehl=peak/flux/factor, where factor varies depending on which filter
is being used. Note that this Strehl is only an approximation, but
should be indicative of the image quality.
In automatic mode, the algorithm finds the FWHM around the peak pixel
in the image (note: sometimes this will find a bad pixel or cosmic
ray, not a real object). In manual mode you will click on the fwhm
button then click on the source in the image. Two circles will be
overlaid on the image around the source, one showing the FWHM fitting
region and another for the photometry calculation region. The radii
for these two functions can be set using the Image Browser Config -
Configure menu (Figure 8). The radial profile and FWHM fit will be
displayed in the Radial Profile window (Figure 7).
Use a similar procedure for the other image sharpening modes to get
the best possible strehl and internal alignment.
Figure 5: Image Browser GUI
Figure 6: Radial Profile display.
Figure 7: Text output.
Config Menu
Figure 8: Configure GUI.
sa@ucolick.org
Last modified: Sat Mar 26 15:11:16 PDT 2016