[en] Several solar prominences, including a fastly evolving prominence (transient event) were observed using an Hα filter ano the 53-cm coronograph of the Kislovodsk high altitude station. A photoelectric magnetograph in conjunction with a specially designed interference filter at lambda 6072 (pass band of 5 A, line blanketing effect in the observed window less than 0.1%) were used to measure precisely the prominence continuum emission produced by Thonson scattering on the free electrons. The integrated along the line of sight number of electrons per unit surface is deduced (about 2.5x10¹⁹ cm^-2) and the total mass of typical prominence is estimated (1x10³⁹ atoms)