we have _pd_meas.rocking_angle, also need _pd_meas.rotation_angle?

[rowlesmr]

working through powder diffraction chapter.

_pd_meas.rocking_angle is defined as

The total angular range, in degrees, through which a specimen is rotated or oscillated during a measurement step (see _pd_meas.rocking_axis).

but if the specimen is rocked 90°, this implies that we then reverse the rotation direction, and go back over the same specimen orientation we just passed, until it goes again, never seeing the other 270° of the specimen. It's a back and forth.

If the the specimen is rotated 90°, then over four consecutive data points we've seen every part of the specimen. Its all in one direction.