Calculate 2D class averages

Using the GUI

For calculating reference-free 2D class averages, select the run-type of 2D averaging from the drop-down menu at the top of the GUI.

Sampling tab

In-plane angular sampling rates of 5 degrees are enough for most applications. Translational search ranges may depend on how well-centered the particles were picked, but often 10 pixels will do the job (translational searches in subsequent iterations are centered at the optimal translation in the previous one, so that particles may "move" much more than the original search range during the course of an entire refinement. Note that pre-centering prior to RELION refinement is not necessary, and also not recommended (it often messes up the Gaussian distribution of origin offsets).

Running tab

It is unlikely one needs threads for 2D class averaging, as this typically takes only modest amounts of memory. Therefore, in case multiple CPUs are available for this task, use the more efficient MPI parallelisation.