We present the recent photometric monitoring of blazar Mrk421, obtained from the Gerostathopouleio Observatoty at University of Athens. Follow-up observations have been performed on this source after a highly energetic flare which occurred on 13 April, 2013. The flare was observed in X- rays by Nustar & Swift and in GeV - TeV gamma-rays by the Fermi satellite and MAGIC/VERITAS telescopes respectively. Continuous photometric monitoring in the optical BVRI bands during 3 months after the flaring activity reveals a quasi-periodic light variation. This is one of the few times that Mrk 421 was observed for such a long period without large observational gaps. We perform Fourier analysis of the almost uninterrupted 3-months-long dataset in order to get insight on the characteristic timescales of the system. We discuss also possible origins of the optical variability by performing cross-correlation analysis of the optical and of the simultaneous X-ray emission detected with XRT onboard the SWIFT orbital satellite.

Selected CCD photometry of the nova forwarded by E. Waagen, AAVSO: Aug. 13.955 UT, [10.2 (G. Murawski, Suwalki, Poland; V-band); 14.817, V = 6.5 (I. Sergey, Molodechno, Belarus); 14.872, V = 6.43 (P. Hallsten, Vasterhaninge, Sweden); 14.876, B = 6.43 (L. Corp, Rodez, France); 14.877, V = 6.11 (Corp); 14.878, R = 5.68 (Corp); 15.837, B = 5.35 (T. Wikander, Borlange, Sweden); 15.883, V = 5.13 (A. Sonka, Bucharest, Romania); 16.037, I = 4.60 (K. Gazeas, Athens, Greece); 16.035, R = 4.71 (Gazeas); 16.033, V = 4.80 (Gazeas); 16.031, B = 4.97 (Gazeas); 16.279, V = 4.44 (A. Oksanen, Muurame, Finland); 16.278, B = 4.82 (Oksanen);

New variable stars were discovered at the University of Athens Observatory, during data reduction in the frame of BVRI CCD observations of the eclipsing variable stars between August 2012 and June 2013. The photometric data were used in order to classify the new variables and calculate their principle photometric properties, such as their orbital period and amplitude of variation. All new discoveries are classified as contact eclipsing binaries of W UMa-type. New times of minimum light are determined and the astronomical ephemeris is calculated for each individual system.

Our recent ground-based BVRI CCD observations of the eclipsing binary system EL Aqr provide the most accurate photometric light variation obtained so far for this system. In addition to the photometric observations, a revision of all existing spectroscopic data is carried out and a new mass ratio is derived. The combined photometric and spectroscopic data are analyzed using the Wilson- Devinney light curve synthesis code and new geometric and photometric elements are calculated. EL Aqr is found to be in contact configuration, showing partial eclipses, and one of the smallest mass ratios ever found on contact binaries.