Polarimetry

It has been very hard to obtain reasonable measurements of polarization standards using the 4 NOTCam Polaroids, and commissioning of these Polaroids has taken quite some time. Based on very few JHKs band measurements of two zero-polarisation standards and two high-polarisation objects (not standards) over two different nights we find that the 2 zero-polarisation standards give 1-1.5 % polarisation in JHKs. This accuracy is probably as good as it gets with the Polaroids (we believe this to be limited by distortions of the Polaroids with respect to their holder as they are cooled down to -200 C). We are currently working on quick-look reduction tools to reduce and analyse observations taken with the Polaroids. Also, a general observing script for polarimetry using the Polaroids is being developed.

We believe that to a dual-beam polarimeter would be the way to go for NOTCam polarimetry, and we will study this option in a bit more detail.