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
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
Set top left of region to
Set top right of region to
Set bottom left of region to
Set bottom right of region to
Set all four corners of
region to trace
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
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".