On Tue, 12 May 2015 17:24:18 -0500, Gerd Rosenbaum <rosenb...@anl.gov> wrote:
... >But no big deal. It's a -1 in one of the axes definitions. There are, as >you stated, many more axes definitions and they depend on the geometry >of the end station. E.g., at the SBC, the orientation of otherwise >identical goniostats is mirror-image between the ID and the BM for >reasons of layout of the two beamlines relative to each other. The idea >that the axes definitions should be uniform is not practical. > Yeah, in principle no big deal, I agree. But the mirror-image concept does not extend to everything: e.g. screws will still be right-handed in the mirror beamline, and motors (in vacuum pumps etc.) will rotate in a given direction in both the beamline and its mirror. Those motors that move devices up/down or left/right may require the other direction in the mirror beamline. The same is true for the spindle motor: if you don't reverse its direction in the mirror beamline, then a user will e.g. not be able to switch measurements of a mounted crystal easily between mirror-related beamlines: s/he will have to use different inputs to data processing programs, and will have to re-index. So yes, the principle is easy to understand, but to make users happy in practice, during beamline commissioning and setup of user operation a conscious decision can and should be made (and yes, I have talked to beamline people who were not aware of this). If that decision is "reverse phi", ok, but this needs to be documented in an accessible way. best, Kay
