Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146 dark cloud complex-a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735 Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability ( V = 1 m · 2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations ( I = 0 m · 3). The analysis of existing photometric data shows a very slow decrease in star brightness-1 m · 8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical plate archives is discussed briefly.

Aims. The main purpose of our investigation is to construct the long-time light curve of the PMS star V 1184 Tau. We consider the study of the photometrical variability of PMS stars as very important for understanding stellar evolution. The unusual photometric variability of V 1184 Tau was reported in previous studies as well, but the nature of the observed deep minima is still under discussion. Methods. We present recent data from CCD photometry and from archival photographic plates. The photometric BVRI data presented in this paper were collected from November 2005 to November 2007. To construct the historical light curve of V 1184 Tau, a search for archived photographic observations in the Wide-Field Plate Database (WFPDB) was made. As a result, 412 photographic plates were found containing the field of V 1184 Tau. A part of the plates were scanned at our request and a magnitude estimation was made of V 1184 Tau. Results. Our recent photometric data suggest that the star brightness is still near the minimum. Thus the period of strong light variations that started in 2003 continues up to the present, hence more than 4 years. Our data from the archival photographic plates suggest that an unknown minimum of brightness exists in the approximate period 1980−1985. Taking all available photometric and spectroscopic data into account we must reject the hypothesis that V 1184 Tau is an FU Orionis type object. V 1184 Tau is a G type low-mass star whose spectrum is similar to WTT stars, but its photometric behavior is typical of the UX Orionis variable stars. Assuming the obscuration from orbiting dust clouds as a reason for a deep minimum, we estimate the approximate period of obscurations and the interval between two deep minima. Our calculations give a 25−28 year period between the two minima and approximately 8−10 year duration of the minima.

Abstract. The current status and future development of the WideField Plate Database, which is in preparation at the Institute of Astronomy in Sofia, are described. The database will be centralized and will provide on-line access to the information on about 2 million photographic observations.

We present observations of the nearby tidal dwarf galaxy Holmberg IX in M81 galaxy group in narrow band [SII] and Hα filters, carried out in March and November 2008 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for resident supernova remnants (identified as sources with enhanced [SII] emission relative to their Hα emission) in this galaxy yielded no sources of this kind, besides M&H 10-11 or HoIX X-1. Nevertheless, we found a number of objects with significant Hα emission that probably represent uncatalogued HII regions.

Abstract. We present a mapping of the large voids (D ≥ 50 h −1 Mpc) in the spatial distribution of clusters of galaxies in the Northern Galactic Hemisphere in a volume defined by galactic latitude b ≥ +30• and redshift z ≤ 0.14. Rich clusters with spectroscopically measured or photometrically estimated redshifts are used as tracers of the large-scale structure of the Universe. An automated void-search and analysis procedure which identifies a void as a system of intersecting empty spheres is applied, allowing for a description of the void dimensions, volumes and shapes more complete than in previous investigations. A number of void catalogues corresponding to different tracer types, different sources of redshift data, and different versions of the search method have been generated and analysed. Visualizations of the 2-D and 3-D distributions of voids are presented. The estimated mean dimensions of the voids of R ≥ 1 and R ≥ 0 Abell/ACO clusters are D e = 105.0 ± 5.6 h −1 Mpc and D e = 87.2 ± 4.1 h −1 Mpc, respectively, where D e is the equivalent void diameter. We have identified the poor clusters, groups, and galaxies populating the voids of rich clusters and constructed radial density profiles of the voids, which show the presence of a void hierarchy.