International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 2.2, p. 35

Table 2.2.5.1 

J. R. Helliwella

aDepartment of Chemistry, University of Manchester, Manchester M13 9PL, England

Table 2.2.5.1| top | pdf |
The distance displacement (in mm) measured on the film versus angular setting error of the crystal for a screenless precession ([\bar\mu=5^\circ]) setting photograph

Angular correction, [\varepsilon], in degrees and minutes[\Delta] r.l.u Distance displacement (mm) for three crystal-to-film distances
60 mm75 mm100 mm
0 0 0 0 0
15′ 0.0175 1.1 1.3 1.8
30′ 0.035 2.1 2.6 3.5
45′ 0.0526 3.2 4.0 5.3
60′ 0.070 4.2 5.3 7.0
1° 15′ 0.087 5.2 6.5 8.7
1° 30′ 0.105 6.3 7.9 10.5
1° 45′ 0.123 7.4 9.2 12.3
0.140 8.4 10.5 14.0

Alternatively, Δ = δ/D [\simeq\sin4\varepsilon] can be used if [\varepsilon] is small [from equation (2.2.5.1)[link]].

Notes

  • (1) A value of [\bar\mu] of 5° is assumed although there is a negligible variation in [\varepsilon] with [\bar\mu] between 3° (typical for proteins) and 7° (typical for small molecules).

  • (2) Crystal-to-film distances on a precession camera are usually settable at the fixed distance D = 60, 75, and 100 mm.

  • (3) This table should be used in conjunction with Fig. 2.2.5.1[link].

  • (4) Values of [\varepsilon] are given in intervals of 5′ as this is convenient for various goniometer heads which usually have verniers in 5′, 6′ or 10′ units. The vernier on the spindle of the precession camera is often in 2′ units.