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The paper discusses the construction of characteristic curves for various astronegatives with a single exposure. Particular attention is paid to the question of extrapolation of the characteristic curve for the region of the weakest stars in the absence of standards. A new method for constructing an individual characteristic curve for digitized films and plates in the UBVR system has been proposed and implemented. The processing of frames of digitized plates and films with sky areas is car- ried out using LINUX/MIDAS/ROMAFOT software tools. ROMAFOT application allows us to extract astro- metric rectangular coordinates X,Y and photometric char- acteristics such as instrumental photometric magnitudes m, FWHM, and the intensity in the center of the star im- age I c for all fixed objects on each astronegative. For all frames, the connection between instrumental photometric values m with stellar magnitudes in any system (Johnson UBVR, Tycho-2 or GAIA catalogs, etc.) is not linear and multipurpose. It is presented as the characteristic curve for each astronegative. Currently, the determination of U, B, V, R magnitudes of stars and other space objects is in pro- gress for astronegatives with the single exposure obtained in the frameworks of selected observational projects.

This work was done to assess the accuracy of the plate processing method and to study in detail the Epson Expression 10000XL scanner, which is used to digitize the FON-Kitab astronomical plates from the photographic archive collection of the Ulugh Beg Astronomical Institute (UBAI) of the Uzbekistan Academy of Sciences. The glass archive of the UBAI has about 15 thousand photographic plates with images of various space objects. To process the plates the specially developed software in the LINUX/MIDAS/ROMAFOT was used. From comparing the results of processing digitized files with grayscale 8 and 16 bits, an assessment of the accuracy of the developed method for determining rectangular coordinates and photometry was made. The Epson Expression 10000XL flatbed scanner together with developed software can be used to digitize and process the astronegatives and obtain characteristics of objects (high, medium and moderate brightness) with an internal accuracy better than 0.05ʺ and 0.015 m for equatorial coordinates and B-magnitudes, respectively. To assess the repeatability of astrometric and photometric errors of the scanner, six consecutive scans of one plate with 600, 900, 1200, 1500, 1800, 2100, 2400 and 2540 dpi spatial separations were processed. The average accuracies of measurements were σ αδ =0.07ʺ for the equatorial coordinates and σ m =0.13 m for B-magnitudes. The results of the xperiments showed that a scan mode with a spatial resolution of 1200 dpi is the best option for plate digitization. Higher resolution scanning modes require a significant increase of digitizing and processing times of a plate, but they do not affect on an accuracy of the obtained results.

The arrivals of the new more accuracy reference catalogues and also development of new meth- ods and approaches for reduction astrometric data give the new life for photographic plates archives. Gaia DR2 is not only a giant step in the astrometric accuracy allowing to measure new objects also provides plates archives ob- served in the past with modern accuracy. In this work we present the first results of astrometric reduction in the sys- tem of Gaia DR2 for some photographic plates that were obtained by UK Schmidt telescope (UKST) and digitized by the SuperCOSMOS scanning machine. The UKST is a classical Schmidt with the following parameters: mirror diameter 1.83m; focal length 3.07m; photographic plate size 356mm square, covering 6.4 x 6.4 degrees of sky; plate scale 67.12 arcsec/mm. To date the UKST has taken over 17,000 plates, the plates are stored in the Plate Li- brary at the Royal Observatory, Edinburgh. The photo- graphic plates are digitized to 15 bits (32768 grey levels) with a resolution of 10 microns (0.67 arcsec)/pixel). Each digitized Schmidt plate has size 32256x32256 pixels and produces about 2 Gbyte pixel data .. We are making new reduction of photographic plates that allowing to provide valuable data for future researches in astrometry as well as in astrophysics. The obtained astrometric and photometric data from photographic plates were compared with same one from modern catalogues.