deletions | additions       diff --git a/At_the_Nasmyth_table_of__.tex b/At_the_Nasmyth_table_of__.tex  index 1472a3b..8288c8c 100644  --- a/At_the_Nasmyth_table_of__.tex  +++ b/At_the_Nasmyth_table_of__.tex 
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\item The tilt and shear measurements from the in-built tilt and shear system in the fringe tracker are used to 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 such  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. The piston term (requirement 4)is also measured using the primary fiducial: the upstream beam is retroreflected off M3 and travels back to the fringe tracker. The delay line positions are adjusted until fringes are seen and the relative position of the delay lines gives the piston term.