Nov. 29 2012, RZ
The reference pixel used for pointings and foci is quite unstable and even changes the position.
The figure below shows the 2mm data after subtraction of a "common mode". The reference pixel 15 (counting from 1 for the 2mm array) shows strong instabilities.
It even does change the position, as shown in the figure below.
This instability affects significantly the focus and pointing results. In the figure below the elev-subscans do not show the source because of this effect and not the variable atmosphere. The source is clearly visible in the upper right image - with a signal as in the azim-subscans.