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4. Conclusions

Near infrared (0.9-2.5 tex2html_wrap_inline1577m) imaging polarimetry of large fields of view (>1 arcmin) with sub-seeing image elongation can be best performed using Wollaston prisms manufactured with AgGaStex2html_wrap_inline1581 or LiYFtex2html_wrap_inline1583. From the optical point of view the best material is AgGaStex2html_wrap_inline1585 because it has larger birefringence and smaller chromatism. However, YLF may be practically more convenient because of its lower refractive index (tex2html_wrap_inline1587 and similar to optical cements), better thermo-mechanical properties and lower price.

New measurements of the transmittance of Calcite at at 77 K indicate that CaCOtex2html_wrap_inline1589 cannot be used for applications at wavelengths tex2html_wrap_inline1591 tex2html_wrap_inline1593m in astronomical polarimeters.

Copyright by the European Southern Observatory (ESO)