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→P1 data collection / Pilatus: update & make more general
(→pick the h+k+l=2n reflections from a primitive dataset: fix echo command) |
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== P1 data collection / Pilatus == | == P1 data collection / Pilatus == | ||
According to the classical paper ([http://dx.doi.org/10.1107/S0907444999008367 Z. Dauter (1999), Acta Cryst D55, 1703]), the required rotation range for native data in space group P1 is 180°, and for anomalous data is 180° + 2 theta_max (theta is the diffraction angle). In the case of the standard geometry (direct beam vertical to, and central upon, the detector), this leads to 2-fold redundancy. <br /> However, experience shows that collection of | According to the classical paper ([http://dx.doi.org/10.1107/S0907444999008367 Z. Dauter (1999), Acta Cryst D55, 1703]), the required rotation range for native data in space group P1 is 180°, and for anomalous data is 180° + 2 theta_max (theta is the diffraction angle). In the case of the standard geometry (direct beam vertical to, and central upon, the detector), this leads to 2-fold redundancy. <br />However, experience shows that collection of more than that is a good idea, as the scaling will be more stable, and there is some leeway to discard radiation-damaged frames at the end of the data set. So we regularly collect 360° for native data unless we have specific reasons to deviate from that rule. <br />The Pilatus and Eiger detectors are composed of many panels, and have horizontal and vertical dead areas. This generally lowers completeness, and the effect is particularly noticeable in low-symmetry spacegroups. Make sure (if necessary, by moving the detector) that the direct beam is not at a crossing between horizontal and vertical dead areas, nor at the middle of a panel, because this prevents symmetry-equivalent reflections from all being unmeasured. | ||