The web pages for polarimetry with ALFOSC have been updated and improved. Sequencer scripts for doing polarimetry have been developed and are fully documented on these webpages.

From test doing linear polarimetry using 4 positions of the half-wave plate it appears that the accuracy seems to be limited to a level of $\sim$0.25%, which might be caused by the two beams following slightly different paths through the optics. One would expect that doing observations using 8 positions of the half-wave plate would provide more accurate results as the different polarization orientations effectively swap paths in the second set of 4 positions. If might even be that the position of the half-wave plate itself effects the result, and observations using 16 positions of the half-wave plate might be needed to provide the most accurate results. This needs to be checked.

Thomas Augusteijn 2008-11-14