Hi Looking at this in a slightly different way:
The Lorentz factor is inversely related to the speed at which the reciprocal lattice points traverse the Ewald sphere; those reflections close to the rotation axis have a speed through the Ewald sphere that is tending towards zero (because they are moving more parallel to the surface of the Ewald sphere), so the Lorentz factor tends to infinity. Not only does the Lorentz factor get huge, but there comes the point computationally when the errors in calculating it get too big to get a meaningful value. (There are also reflections that appear on the diffraction image even closer to the rotation axis that are due to reciprocal lattice points that are predicted to never completely cross the Ewald sphere, and these are not even marked by a green prediction.) I imagine this sometimes as a meteoroid skimming across a planet's atmosphere (carrying straight on rather than bouncing off, perhaps passing through some of the atmosphere) but never reaching the surface (the thickness of the atmosphere would correspond to the thickness of the Ewald sphere). A meteoroid (moving at the same speed) encountering the atmosphere at an angle closer to 90ยบ would pass through the atmosphere more quickly. This may or may not help... On 14 Dec 2016, at 08:33, Tim Gruene wrote: > Dear Walt, > > reflections close to the rotation axis stay in reflecting condition for a > long > time, where time is sensibly measured in degrees. Their intensities cannot be > determined reliably, and I would think that most integrating programs, > including HKL2000, reject such reflections. > > Best regards, > Tim > > > On Wednesday, December 14, 2016 10:40:31 AM Hank wrote: >> Dear CCP4BB users, >> >> I have a question about Mosflm. The manual says green predictions have >> "reflection width greater than 5 degrees" and will not be integrated. I >> always >> assumed it should have something to do with Lorentz factor but not quite >> sure. >> Why is it so? I'm not aware of such geometrical restriction in HKL2000. >> Thank you! >> >> Walt > -- Harry -- Dr Harry Powell Chairman of International Union of Crystallography Commission on Crystallographic Computing Chairman of European Crystallographic Association SIG9 (Crystallographic Computing)
