The single-channel photometer-polarimeter at Sanglok Observatory was built at the
Institute of Astrophysics of Tadjik Academy of Sciences. It allowed
quasi-simultaneous photometric and polarimetric observations. The useble wavelength
range was 0.35-0.75 microns. The polarimeter worked on the modulation principle with
a rapidly-rotating polarizer as the analyzer. The rotation frequency of the polarizer
was about 33 revolutions per second. Four impulse counters were used to registrate
impulses during each quarter of a polarizer revolution. The total number of impulses
in four positions of the polarizer allow the derivation of the values of the Stokes Q
and U parameters and hence the value of the degree of linear polarization and the
position angle. The observing procedure included consecutive measurements of an
object and a sky background near the object with the same diaphragm.  To control the
stability of instrument operation the measurements of a built-in signal generator
were used.

For more information, see

Kayumov V.V., Kiselev N.N., Pushnin P.A., Rakhimov V.Yu., Siklitskij V.I., Tarasov
K.V., Chernova G.P., Yakutovich V.N. The investigation of the photometer-polarimeter
of the 1-m RCC telescope. Bull. Inst. Astrophyz. Tadjik Acad. Sci No. 78, p. 10-16,
1989 (in Russian).