## Checkpoint

### which two layer-lines (LL) were used?

Note, there may be multiple acceptable answers to this question. Format: LL (R, Z)

LL (36, **30**)

LL (23, **156**)

Hint: LL (27, **186**) = LL (36, **30**) + LL (23, **156**).

The distance of LL(27, 186) to meridian is between LL(36,30) and LL(23,156). This suggests LL (36, 30) is probably has a different hand to LL (23, 156)

### What are the possible Bessel order ranges for those two vectors?

LL (36, 30)
:

2*π*R*rmax = 2 * 3.14 * (36/640/1.12) * 30 = 9.4 Bessel order n ≤ 8

LL (23, 156):

2*π*R*rmax = 2 * 3.14 * (23/640/1.12) * 30 = 6.0 Bessel order n ≤ 5

### What are the possible symmetries?

### What's the correct symmetry (quickly check whether it is in your list)

point group: C3

helical rise: 2.10 Å

helical twist: -54.7 degrees