Re: [ccp4bb]: dodgy indexing

[Gosu RamaChandraiah <gosu@prism.mbu.iisc.ernet.in>]

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	hi,

	In denzo, mosaicity is defined as the smallest angle through which
the crystal can rotate about an axis or combination of axes while a
reflection  is still observed.

	From this definition, we can extend our logic for single crystal
oscillation photography...

  delta phi = ( longest reciprocal cell / d*min)(180/pi) - mosaicity


	     mosaicity should be smaller than the first term so that delta
phi remains a positive quantity.
	     
	     If crystal is highly mosaic, oscillation angle(delta phi) 
should have been very small while collecting the data. Or else at the time
of processing one has to select a shell of reflections to start indexing
from equation mentioned above. 

	With regards
	GOSU

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On Tue, 27 Feb 2001, Lauris Kemp wrote:

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> ***    CCP4 home page http://www.dl.ac.uk/CCP/CCP4/main.html    ***
> 
> Hello
> I'm trying to index a data set with denzo. The problem is with
> mosaicity-it looks about 1 but at this value it misses out some low
> resolution spots and seems to overfit for the number of spots at high
> resolution. Thought it might be misindexed but did a direct beam shot
> and the beam values look about right. It manages to autoindex it fine
> and the chi values are also fine.
> Lauris
>