description: CONICA is equipped with a MgF2
Wollaston prism, used for imaging polarimetry, as well as a turntable
half-wave plate. The Wollaston prism is located in the OPTI4 filter
wheel (INS.OPTI4.NAME=Wollaston_00). Since the J-band filter is in the
same wheel, J-band polarimetric observations are not possible. Also,
the half-wave plate is installed in the CONICA's entrance wheel, where
the calibration mirror is situated. Thus, internal calibrations with
the half-wave plate cannot be done.
Wire grid polarimetry and the Wollaston_45 are no longer available (as of P82).
The Wollaston splits the incoming light into ordinary and
extraordinary beams. An image taken with the Wollaston prism will
contain two images of every object. To avoid sources overlapping a
special mask consisting of alternating opaque and transmitting stripes
is inserted in the optical path.
An example of the polarimetric observation with filter H, camera S27
Polarimetric observations with filter Ks and camera S13. No Mprime observations are offered with polarimetry.
This mode is offered in service and visitor mode. It is not supported by the pipeline.
calibrations:The calibration plan includes
standard detector darks with readout mode and DIT matching the one used for science;
standard sky (twilight) flat fields without the polarimetric mask
mask and without the polarizer; In VM twilight flats with half-wave
plate can be requested; No internal lamp flats are offered, as the
calibration mirror in the light path changes the level of
polarization.