To make a section (cut) along a line, check to make sure that the
status (next to the color scale) reads `Section: line'; if not,
select "Section type" from the main menu and "Line" from the
roll-out submenu.
Then move the cursor to the red dot at the center of the image. Hold down the middle mouse button to drag the red dot. An image spot near the cursor is magnified in the zoom subwindow in the lower right corner, following the movement of the mouse. (The magnified spot shows individual pixels in a full 2500x2500 or 3000x3000 plate image as square cells.) A red line overlaying the image connects the large moving dot with the smaller dot which remains at the center.
The corresponding linear section of
image intensity is plotted (in red) in the cut and profile subwindow
at the bottom of the screen.
The horizontal scale is adjusted so the section just fills the subwindow. Note that the left edge of the cut and profile subwindow corresponds to the center dot in the image.
The vertical scale is logarithmic, with a horizontal rule at each decade.
The coordinates of the line end point (in pixels of the full image) and the intensity value are displayed in the panel between the image and the cut and profile subwindow. Also shown are the values of the reciprocal space coordinate q (in units of inverse Å), the spacing d (in Å), the angular coordinate theta (in degrees), and the (in-plate) azimuthal angle psi (in degrees) of the line end point.
To make fine adjustments of the line position, use the arrow keys to move the solid red dot in increments of one pixel on the screen image. (The screen image of a 30 cm plate is reduced to 1/5 the size of the full image, from 3000x3000 to 600x600 pixels on the screen image; for a 20 cm plate, the full 2500x2500 image is reduced to 1/4 size, i.e. 625x625. For a CCD image, there is no reduction of the image: 625x576 pixels are displayed.) For the plate images, each one pixel step on the screen image moves the line end point five (or four) steps in the full image, as seen in the zoom subwindow.
When holding down a Shift key, the arrow keys move the line end point in coarser steps of 5 pixel on the screen, i.e. 25 (or 20) pixels in the full image.
The line end points are positioned in the screen image, so for the plate images, line end point coordinates are always multiples of 5 (or 4); points along the line are sampled from the full image.
To make a section (cut) along the circumference of a circle, select
the option "Section type" from the main menu, then select
"Circle" from the roll-out submenu.
The status line should now
read `Section: circle'. Drag the solid red dot by holding down
the middle mouse button. This dot positions the circumference.
The section is displayed, in place of the line cut, in the cut and profile
subwindow, with the horizontal scale adjusted so the full 360 degree
cut just fits in the subwindow. The left edge of the cut-and-profile
subwindow corresponds to the position of the dot on the circumference,
and the section is taken in the counterclockwise direction.
If portions of the circle fall outside the image, they will be skipped in building the section. There will be no gaps within the section plot, but the plot will not extend across the entire cut and profile subwindow, whose width always corresponds to 360 degrees.
Integrated profiles are shown in the cut-and-profile subwindow together with a line cut, using the same horizontal scale; but a circle cut temporarily suppresses display of the integrated profiles.
The Tab key controls which endpoint of a line, or which reference point on a circle, is movable. The solid dot is movable with the mouse or arrow keys. Hit the Tab key once to make both dots solid. The second status line near the color scale should read `Movable: both'. Now either dot can be dragged with the mouse; the arrow keys now move both solid dots together.
Hit the Tab key again to make only the central dot movable; hitting the Tab key a third time returns to the original state, with only the larger dot movable.
If you move the smaller dot away from the center, and later wish to return it to the center, use the main menu option "Move to Center" and then select "Line", "Circle", or "Rectangle" from the roll-out submenu.
The central point itself can be redefined using the "New Center of Image" option in the "Zoom Options" menu.
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