To trace a plate spectrum, first load the
picture into the overlays
window, so it looks something like the picture below. (You can load the
picture by copying and pasting from another application or loading
image files directly.)
1. Determining Plate Angle
The plate is unlikely to be scanned perfectly vertically, and this is
not a requirement for accurate operation.
The angle must be measured, by selecting a single clear line with the
mouse as follows:
Press "Operate" and then "Plate Angle" to display and set the plate
angle. (It is recorded as one of the settings for the overlay.)
2. Select Region to Scan
Select the region to trace by pressing the following buttons in turn:
Set top left of region to trace
Set top right of region to trace
Set bottom left of region to
Set bottom right of region to
Set all four corners of region
After pressing one of the above, press the mouse button on the required
point. The "Cancel" button can be used to stop the process. The "Top"
points define one edge of the trace area; the "Bottom" points are only
used to define the line at which the trace stops. (The "Top" line does
not have to be above the "Bottom" line.) To trace the main spectrum
above the window should look something like this:
and for the calibration lines:
3. Perform the Scan
Select "Operate" and "Plate" to do the scan. An additional overlay will
be generated each time you do this; the vertical scale is the average
of the intensity along the lines determined by the plate angle. The
horizontal scale is the pixel value where this line passes through the
centre of the image, so that each spectrum traced from the same image
will be on a consistent horizontal scale.
The standard calibration procedure can
now be used. Note that if you use separate calibration traces you
should use "Apply Calibration To"
to transfer the calibration from one overlay to another rather then "Copy Frequency to".