Is the Beam Center Correct?
We have had a couple of instances when the beam center was incorrect in the header of our images. The header of an image is written out when you collect a diffraction image. The header may contain the wavelength, collection time, beam center and oscillation step size, which are read by data processing software (in this case Ipmosflm).
Unfortunately, the information contained within the header may not be correct.
How can you look for to tell if your beam center is incorrect?
One way is by looking at where the Bragg reflections are predicted vs. where they actually are located. It is important to check if the orientation of the lunes and the spacing between Bragg reflections looks reasonable. If they are not then you may an issue with your unit cell and/or space group and not a beam center problem.
If you are having trouble seeing the offset in the video here is a screen shot:
The blue arrow is pointing toward the Bragg reflections while the red arrow indicates the predicted reflection locations. Also you can see that there are fewer Bragg reflections (dark spots) than what is predicted (yellow squares) which is a sign that there is a problem.