The Zoom Window provides a close-up view of a small region of the ccd.
Contents
Using the zoom window
The zoom window is automatically opened at start up.
If it is closed or hidden, it may be brought back to the front by
selecting the tools menu,
zoom... option from the
main menu.
The zoom window allows you to examine a small area of
the image. The size of the zoomed in region is set by the
size box. The location of the region is set by double
clicking on a point in the zoom display, in the main-display window, or in
the values window; it can
also be set by setting the cursor position in the
main-display window, in
the zoom display, or in the values window, and then
pressing the button with the cursor symbol in the zoom
display. (It is no longer possible to manually set the the location of
the zoom box.) The stretch can be adjusted by entering new
limits, just as in the main-display window; it can
also be set by using the Zoom
Str. button in the main-display window.
The cursor position may be set by using the
mouse, and single clicking on a point. The x, y, and pixel value of
the current position are displayed in the X-Y box. Note that single
clicking on the main-display
window will also set the cursor position for the zoom
window and the values
window and vice versa. (For releases before 2.07, the zoom window
and main-display window
had different cursor positions; and the values window had no cursor
position at all.) You may change the current position by entering
values in the X and Y coordinate boxes; however, if you don't type a
carriage return when you are done, nothing will happen.
Note that the size of the zoomed in
area is only approximately what is set via the size box. The
actual size is modified in order to insure that the aspect ratio is
correct and is limited to be smaller than the size of the ccd.
Special features
The FWHM button attempts to fit a Gaussian to what is
in the zoom window, and returns the width and height of the Gaussian.
The algorithm used is not
very robust; the user must always check the plot to make sure that
the fit is reasonable. The user must make sure that the region that is
in the zoom window contains only a single peak. The region may not
contain any hot pixels or cosmic rays. The region must be much wider
than the peak; the points on the edge of the region must be at the
background level. The algorithm will be replaced by an improved
algorithm when time permits.
The stat button displays the mean and standard
deviation of the data that is in the zoom window. It also produces a
rough histogram of the values. The histogram is automatically scaled
to have a half width of three standard deviations. The
median button performs the same calculations, but also
provides the median, which can take a long time to calculate for a
large region.
The Print button prints the region of the plot that is
visible in the zoom window. The zoom size should be as small as
possible, as this will reduce printing time. The printing algorithm
will be replaced by an improved algorithm in a later version. Note
that the main menu print command is much
faster than this button, but gives slightly poorer image quality.
This document was written by Hubert Yamada (yamada@ifa.hawaii.edu) and Kevin Jim (kjim@terrasys.com).
