Resolution Limits?

[Hakon Hope]

This has to do with our tendency to prefer round numbers. The 
"resolution" is very often determined by 2theta(max). For 2theta(max=60 
deg, the calculated resolution will be the wavelength.

Resolution is not a sharply defined quantity, so you are right: there is 
some measure of "arbitrariness." Normally it is well-reasoned 
arbitrariness of no great scientific consequence.

Hakon Hope