Upgradation of AIMPOL Instrument on the 104-cm Sampurnanand Telescope of ARIES

Abstract

We present a recent upgradation of the ARIES IMaging POLarimeter (AIMPOL) mounted on the 104[Formula: see text]cm Sampurnanand telescope of ARIES, Nainital since 2004. AIMPOL is upgraded by replacing the older detector with a new CCD, Pylon 1300B and the older sliding filter assembly with an automatic wheel filter assembly. A characterization of this CCD is performed and several CCD parameters like gain, read-out noise, dark current, and linearity are verified. The average value of the bias offset is measured to be ∼600 ADU whereas the dark current is measured to be 0.2[Formula: see text]e−/pixel/h at [Formula: see text]C. The CCD can be operated safely between [Formula: see text] C to [Formula: see text]C due to the almost constant dark current in this temperature range. The nonlinearity of the CCD is measured to be ∼2%, which is suitable for scientific observations. A few polarimetric observations are also taken using the upgraded AIMPOL. The degree of polarization and position angle of a few standard polarized stars are found to be similar to their standard and previously observed values.