The left model shows a silicon cluster a few unit-cells
across. A "flat Ewald slice" (kinematic electron diffraction pattern) of its
corresponding reciprocal lattice is on the right. The bright central
spot in the reciprocal space model is the "DC peak" (unscattered beam).
Camera constant for the diff pat is 1000 [pmA], meaning that you
divide the spot measurement in pm (*pattern model* units
obtained by double-clicking spot pairs with ZOLZ toggled to
show the full reciprocal lattice)
into 1000 to get the corresponding
d-spacing in Angstroms.
If you prefer to measure from
the captured diffraction image in pixels, the camera constant
is near 150 [pxA] although it has not been
measured carefully.

*Challenge*: Try capturing a <110> zone diffraction
pattern, and indexing the spots in it. This
calculator might come in handy if you
first type two numbers
(e.g. 10 and 100) that multiply to 1000 into the calibration
text boxes so that *pattern model* units substitute for mm.