deletions | additions       diff --git a/At_the_Nasmyth_table_of__.tex b/At_the_Nasmyth_table_of__.tex  index b8f3fe7..1472a3b 100644  --- a/At_the_Nasmyth_table_of__.tex  +++ b/At_the_Nasmyth_table_of__.tex 
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Space does not permit a full description of the start-of-night tilt and shear re-alignment procedure (satisfying requirement 2), but it can be split into two phases:  \begin{enumerate}  \item The tilt of the upstream primary fiducial is measured by the FTT and the shear is measured by the UTM shear measurement camera. These measurements are used to (a) align the primary fiducial with the delay-line mechanical axis by adjusting the MOB and (b) to redirect the primary fiducial, aligning it with the UTM inner axis, by adjusting M4 and M5 (this is the "tilt-and-shear algorithm").  \item The tilt and shear measurements from the in-built tilt and shear system in the fringe tracker are used to align redirect  the primary fiducial so as to align it  with the fringe tracker, making use of M11 and M12, the switchyard mirrors. \end{enumerate}  The combination of these phases is designed to ensure that a light beam can travel from the telescope to the fringe tracker so that the errors in the tilt and shear are within the error budget at the start of the night. To keep within this error budget for the duration of the night (requirement 3), the BEASST system uses a fraction of the starlight when observing bright stars to measure any changes in the tilt and shear of the beams and applies appropriate corrections.