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تسجيل مستخدم جديدAccurate photometry with digitized photographic plates of the Moscow collection
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Photographic plate archives contain a wealth of information about positions and brightness celestial objects had decades ago. Plate digitization is necessary to make this information accessible, but extracting it is a technical challenge. We develop algorithms used to extract photometry with the accuracy of better than ~0.1m in the magnitude range 13<B<17 from photographic images obtained in 1948-1996 with the 40cm Sternberg institutes astrograph (30x30cm plate size, 10x10deg field of view) and digitized using a flatbed scanner. The extracted photographic lightcurves are used to identify thousands of new high-amplitude (>0.2m) variable stars. The algorithms are implemented in the free software VaST available at http://scan.sai.msu.ru/vast/
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We initiated digitization of the Moscow collection of astronomical plates using flatbed scanners. Techniques of photographic photometry of the digital images were applied, enabling an effective search for new variable stars. Our search for new variab
les among 140000 stars in the 10 x 5 degrees northern half of the field centered at 66 Oph, photographed with the Sternberg Institutes 40-cm astrograph in 1976--1995, gave 274 new discoveries, among them: 2 probable Population II Cepheids; 81 eclipsing variables; 5 high-amplitude Delta Scuti stars (HADSs); 82 RR Lyr stars; 62 red irregular variables and 41 red semiregular stars; 1 slow irregular variable not red in color. Light elements were determined for periodic variable stars. We detected about 30 variability suspects for follow-up CCD observations, confirmed 11 stars from the New Catalogue of Suspected Variable Stars, and derived new light elements for 2 stars already contained in the General Catalogue of Variable Stars.
At the Hamburger Sternwarte an effort was started in 2010 with the aim of digitizing its more than 45000 photographic plates and films stored in its plate archives. At the time of writing, more than 31000 plates have already been made available on th
e Internet for researchers, historians, as well as for the interested public. The digitization process and the Internet presentation of the plates and accompanying hand written material (plate envelopes, logbooks, observer notes) are presented here. To fully exploit the unique photometric and astrometric data, stored on the plates, further processing steps are required including registering the plate to celestial coordinates, masking of the plates, and a calibration of the photo-emulsion darkening curve. To demonstrate the correct functioning of these procedures, historical light curves of two bright BL Lac type active galactic nuclei are extracted. The resulting light curve of the blazar 1ES 1215+303 exhibits a large decrease in the magnitude from $14.25^{+0.07}_{-0.12}$ to $15.94^{+0.09}_{-0.13}$ in about 300 days, which proves the variability in the optical region. Furthermore, we compare the measured magnitudes for the quasar 3C~273 with contemporaneous measurements.
We present the results of determination of Plutos positions derived from photographic plates taken in 1930 - 1960. Observations were made with Normal Astrograph at Pulkovo Observatory. Digitization of these plates was performed with high precision sc
anner at Royal Observatory of Belgium (ROB Digitizer). Mean values of standard errors of plate positions (x,y) lie between 12 and 18 mas. The UCAC4 catalogue was used as an astrometric calibrator. Standard errors of equatorial coordinates obtained are within 85 to 100 mas. Final table contains 63 positions of Pluto referred to the HCRF/UCAC4 frame.
Online Digital Sky Survey (DSS) material is often used to obtain information on newly discovered variable stars for older epochs (e.g. Nova progenitors, flare stars, ...). We present here the results of an investigation of photometry on online digita
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We identify 339 known and 316 new variable stars of various types among 250000 lightcurves obtained by digitizing 167 30x30cm photographic plates of the Moscow collection. We use these data to conduct a comprehensive test of 18 statistical characteri
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