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.

{{attachment:IDCSJ1426_NIKA2mm-20121124s177-medRPonRPinstable.png | instability of the 2mm ref. pixel #15}}

It even does change the position, as shown in the figure below.

{{attachment:FoV_2mm.png | FoV@2mm}}

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.

{{attachment:3C454.3_NIKA2mm-20121125s204_point_psn_YES_0.png | instability of the ref. pixel during a pointing}}