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We present the first high accuracy UBVRI(RI)c CCD light curves of the poorly investigated eclipsing system V680 Mon = GSC 7428 218 (P = 8.54d, V = 10.02m). They were used to find the photometric solutions and to derive the physical characteristics of the components. The highest known eccentricity e = 0.613 was found in the class of systems with eccentric orbits. The orientation of the orbital ellipse ω = 357° is not convenient for apsidal motion investigation. High accuracy of our observations allows to find the reliable parameters of the system: M1 = 3.3 $${{M}_{ \odot }}$$ (B7 V), M2 = 1.8 $${{M}_{ \odot }}$$ (A2 V). We estimate the age of the components to be 70 mega-years. The photometric parallax π = 0.00109(1)″, derived from our observations, is two times smaller than the value π = 0.0025(9)″ from GAIA DR1, affected by the presence of the K3 V optical companion of the investigated star. The light curves solution demonstrates the presence of a third light, which can be assigned to a star of A4 V spectral class. The light time effect is found in the minima timings, so the source of the third light is physically connected to the eclipsing system. The parameters of the third body orbit are derived.

We present the first high accuracy UBVRI(RI)c CCD light curves of the newly discovered eclipsing system PS UMa = GSC 4375 1733 ($$P = 9_{·}^{d}27$$, $$V = 12_{·}^{m}42$$). The photometric solutions are found, the physical parameters of the components are derived. The eccentricity of the orbit was found to be negligible e = 0.074, which made it difficult to measure the rate of the apsidal rotation. High accuracy of our observations allowed us to find the reliable parameters of the system. Components (Sp = F7 + G1) have advanced significantly in their evolution, the age of the system is 2.4 billion years. The mass and the radius of G1 component is larger and it is ahead of the F7 component in its evolution. The model of the system best suits the theory in the absence of the overshooting in the core. Obtained from our observations photometrical parallax π = 0$$_{.}^{\prime\prime }$$00102(2) coincides with GAIA DR2 value $$\pi =0_{·}^{\prime\prime }00106(3)$$ within their errors. The new EW type variable with period $$ \approx {\kern 1pt} 0_{·}^{d}40$$ was found in the field of PS UMa.

The first high-accuracy CCD UBV RI (RI)C light curves of the recently discovered eclipsing binary V2647 Cyg = GSC 3612 1565 ( ) have been obtained. The photometric light curves are solved and the physical parameters of the component stars are derived. The orbit of the binary is circular, not eccentric as previously thought. Its period is two-thirds of the previously accepted value. The high accuracy of the observations has made it possible to determine reliable parameter for the binary. Obtained photometric parallax is , in full agreement with the GAIA direct parallax measurement. If the optical companion at an angular separation of is gravitationally bound to the binary, the system should be considered hierarchical.

The first high-accuracy CCD UBV RI(RI)C light curves for the recently discovered eclipsing binary V798 Cep (P = 16 d .08, V = 11 m . 8) are presented; this star is included in our program of eclipsing systems with considerable eccentricities. A photometric solution for the light curves and physical characteristics of the component stars are derived. The orbital eccentricity is quite high, e = 0.437. The longitude of periastron is close to 180°, making studies of the apsidal motion difficult. V798 Cep may be a hierarchical system.

We present the first estimates of the relative and absolute parameters of the eclipsing binary EQ Boo based on a light-curve analysis (P = 5.43d, V = 8.8m). This star is simultaneously Component A of the visual binary ADS 9422 (spectral types F7V + G0V; separation of the components 1.3″; magnitude difference 0.7m). The derived disagreement between the components’ physical parameters and the assumption that they have the same age can be removed if there is a fourth, late-type star in the system. This is also able to explain the observed anomaly in the behavior of the O-C residuals at times of minima.

We have obtained the first UBV(RI)C photoelectric light curves of the recently discovered eclipsing binary BD +66 1663 = GSC 4479 412 (P = 7.04d, V = 10.14). We have derived relative and absolute parameters of the binary, and analyzed the interstellar extinction towards the object. Though the star is located in the field of the young open cluster Be 59, we demonstrate that it is not a member.

We have obtained the first U BV R photoelectric light curves for a recently discovered eclipsing binary with a period of 9.33d and an appreciable eccentricity (e = 0.08). We have used these data to determine the photometric elements of the system for a model with two spherical stars with linear limb darkening. The high accuracy of the observations enabled determination of the absolute parameters of the components using available calibrations. The masses of the components are 1.28 and 1.08 M⊙, and their ages are two billion years. The present orientation of the orbital ellipse is unfavorable for studies of the apsidal rotation, which is essentially due to relativistic effects.

High-precision WBVR photoelectric observations of the eclipsing binary GG Ori (B9.5V+B9.5V), which has an eccentric orbit (e=0.22), were carried out in 1988–2001 at the Moscow and high-altitude Tian-Shan Observatories of the Sternberg Astronomical Institute. The aim of these observations was investigation of the apsidal motion of the system. Analysis of the resulting 12-year series of observations enabled us for the first time to accurately (to within 11%) measure the rate of rotation of the orbit $$\dot \omega _{obs} = 0.046 \pm 0.005^\circ /yr$$ and to appreciably improve estimates of the photometric and absolute parameters. The observed value of $$\dot \omega _{obs}$$ is 28% higher than the theoretical prediction of $$\dot \omega _{th} = \dot \omega _{cl} + \dot \omega _{rel} = 0.036 \pm 0.001^\circ /yr$$ . The relativistic part of the apsidal motion in this system $$\dot \omega _{rel}$$ is a factor of 2.5 greater than the classical term $$\dot \omega _{cl}$$ due to the tidal and rotational deformations of the components. The interstellar extinction in the direction of the star (at a distance of r=425 pc) is very large (A v =1.75 m ). A number of recently published results (in particular, the conclusion that the components of this eclipsing binary are young) are confirmed.