Accuracy of ± 0.02° 2-theta.
Minimal FWHM = 0.14 to 0.20° 2-theta may suffice.
Minimal FWHM lowered to 0.08-0.04° 2-theta with correct set of slits.
Kalpha-1 is better but Kalpha-1,2 works too.
Counting step should be as low as 0.02-0.01° 2-theta.
All this is possible on a conventional X-ray powder
Synchrotron can do far better with FWHMs as low as 0.008° 2-theta.
Neutron powder diffractometers cannot offer comparable
Minimal FWHMs are near of 0.12 or 0.20 or even 0.30° 2-theta depending on the instrument
Two techniques are useful in the objective of collecting perfect data for indexing purposes :