Fig. 1. 2.16-m telescope

Fig. 2. A camera of a iKon-L DZ936 CCD (a) and its quantum efficiency curve (b)

Fig. 3. Transmittance curves of the Johnson/Bessell UBVRI filter system

Fig. 4. Schematic diagram of a dual-channel time-division imaging polarimetry

Fig. 5. Schematic diagram of the overall structure of the 2.16-m telescope polarimeter

Fig. 6. Schematic diagram of the optical path of linear polarization photometry (a) and multicolor photometry (b) of the 2.16-m telescope polarimeter

Fig. 7. Internal composition of the polarimeter

Fig. 8. Flow chart of the polarimeter

Fig. 9. Schematic diagram of a target brightness change curve when the polarizer is rotated

Fig. 10. Flow chart of polarization calibration

Fig. 11. Flow chart of polarization measurement

Fig. 12. Flow chart of multicolor photometry

Fig. 13. Schematic diagram of the proposed polarization calibration

Fig. 14. The polarimeter was installed on the focal unit of the 2.16-m telescope for on-sky testing

Fig. 15. The polarimeter observed unpolarized standard target HD14069 (a), polarized standard targets BD+64°106 (b) and VI Cyg #12 (c). An FOV of the image is about 4.63′×4.63′, the pixel scale is 0.54 (″)/pixel

Fig. 16. The polarization of the unpolarized standard target HD14069 (a), polarized standard targets BD+64°106 (b) and VI Cyg #12 (c) measured multiple times

Fig. 17. Landolt equatorial standards of 98 581, 98 L1, 98 580, 98 556, 98 557, 98 563 observed by the polarimeter

Fig. 18. Exposure times with respect to V-band magnitudes when SNR is about 141