Re: [ccp4bb]: ...Replies: Data Reduction for mosaic crystals...

[Jim Pflugrath <jwp@RigakuMSC.com>]

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Perhaps there is no lively discussion on fine phi-slicing because everyone
basically agrees.  Tassos, Pierre, Ed, and Harry have all said about the
same thing.  From an article mentioned by Harry  (Pflugrath, Acta Cryst.
(1999) D55, pp. 1718-1725):

    "There is no advantage to ever-thinner rotation increments per image.
    If the crystal mosaicity is less than 1 deg, then use 0.5 deg per
    image.  Otherwise, use one-half of the crystal mosaicity.  If this
    still results in spatial overlaps, reduce the rotation increment, but
    remember that for large crystal mosaicity values, reflections will be
    spatially inseparable no matter how small the rotation increment."

As for helping Raji, I've looked at her images.  The images exhibit some
problems with crystal splitting or twinning and a mosaicity of well under
2 degrees, perhaps even as low as 0.3 degrees, so her idea of using 0.1
degree images seems helpful in this case.