Moscow Astronomical Plate Archives:
Contents, Digitization, Current and
Possible Applications
N.N. Samus1,2, L.A. Sat1,
S.V. Vereshchagin1, A.V. Zharova2
1Institute of Astronomy, Russian
Academy of Sciences, 48, Pyatnitskaya Str., Moscow 119017, Russia
2Sternberg Astronomical Institute, Moscow University,
13, University Ave., Moscow 119899, Russia
Presented at
the international workshop "Virtual Observatories: Plate Content
Digitization, Archive Mining and Image Sequence Processing", Sofia, April 2005
Abstract. We describe the astronomical plate
archives in Moscow and Zvenigorod and the existing digitization
projects. The collection at Sternberg Institute has very valuable parts that
can be applied to studies of variable stars and external galaxies and still
contain much important information never used yet.
1 Introduction
Regular photographic
observations of the sky for variable-star studies were started in Moscow in 1895.
Since then, several different telescopes were used to take direct sky plates
in and near Moscow, for astrometry and for astrophysics. The Moscow plate
archive also contains very important series of direct photographs and
objective-prism plates taken at the Sternberg Institute's observatory in Crimea. The direct-plate
archive of the Zvenigorod Observatory (Institute of Astronomy of
the Russian Academy of Sciences) is less rich but also contains several thousand
plates.
2 The Plate
Archive of the Sternberg Institute
The contents
of the most important Moscow astronomical plate archive, that of the Sternberg Astronomical
Institute, was briefly presented in Shugarov et al. [1] in 1999. Since then,
the information has been considerably improved. We present its new version in
the Table (N is a somewhat rounded
number of plates) (In this preprint,
the Table was revised compared to the presentation in Sofia and is now still newer
compared to [1]). Besides the plate series listed
in the Table, the plate archive contains several additional, minor and less
important, plate and film series.
THE MOSCOW PLATE COLLECTION (STERNBERG INSTITUTE)
|
D, cm
|
F, cm
|
Field size, deg
|
mlim
|
Years
|
N
|
Site
|
|
10
|
64
|
20´28
|
13
– 14
|
1895
– 1933
|
1100
|
Moscow
|
|
16
|
82
|
16´22
|
14
|
1933
– 1956
|
2700
|
Moscow
|
|
23
|
230
|
6´6
|
|
1955
– 1991
|
10000
|
Moscow etc.
|
|
38
|
640
|
1.4´1.4
|
14
|
1902
– 1972
|
6400
|
Moscow
|
|
40
|
160
|
10´10
|
17
– 18
|
1948
– 1996
|
22300
|
Kuchino (near Moscow), Crimea
|
|
50
|
200
|
3.5´3.5
|
18
– 19
|
1958
– 2004
|
10000
|
Crimea
|
|
50
|
200
|
Spectra
|
|
1959
– 2004
|
2300
|
Crimea
|
|
70
|
1050
|
0.6´0.6
|
13
– 18
|
1961
– 1995
|
9500
|
Moscow
|
All the plates of the Sternberg Institute's collection are kept in
sufficiently good conditions, in the vertical position. Some of them (mainly
old plates) are in wooden boxes with individual places for each plate, other
plates are in card-paper boxes, with soft-paper separators.
The main part of the Sternberg Institute's plate collection, that
on variable stars, is kept at Sternberg Institute by a joint team from the
department of Galaxy and variable stars of the Sternberg Institute and from
the department of unstable stars and stellar spectroscopy of the Institute of Astronomy (Russian Academy of
Sciences). The information on these plate series in the Table is quite
reliable. Other parts of the collection belong to the Sternberg Institute's
department of astrometry and to other teams, we used the information provided
by the plate owners. In the description below, we mostly deal with the
variable-star plates.
The historically-valuable part of the collection are plates taken
with a small equatorial camera with different lenses in 1895--1956. There
exist many different plate centers, with overlapping fields and relatively
few plates for each of the centers. In the earliest period of the collection,
attempts were made to additionally process plates with special chemicals, to
ensure better stability of the photographic layer. Currently, we find no
difference between the plates thus processed and the rest of the plates:
almost no aging problems are detectable among the old Moscow plates.
Obviously, the most scientifically important part of the Sternberg
Institute's plate collection are the plates taken with the 40-cm (F=160 cm) astrograph (installed in
1948 in Kuchino near Moscow, moved to Crimea in mid-1950s). This is the astrograph first installed, on the
initiative of Prof. C. Hoffmeister, at the Sonneberg Observatory, Germany
(where it was called the GA astrograph), in 1938 and taken by the Soviet
Union from Germany in 1945 as a part of the war reparations. The telescope's
position in Crimea was better than in Sonneberg (to the south in latitude,
better weather), and the number of plates taken per year, with a typical
exposure time of 45 minutes, approached 900 for the most successful years
(see the distribution in Fig.~1). The plates of the astrograph series kept in
Moscow are generally of excellent quality and permit detailed studies of
many variable stars. The main part of the collection are variable-star
fields, from the North Pole to declinations about –30o, with up to
500 plates per field. For variable stars that can be found in several fields,
sometimes we can get as many as 1000 photographic observations. The typical
exposure time for the variable-star fields was 45 minutes. The plate limit
for such exposures, originally about 17.5–18m in a system close to
B, gradually somewhat deteriorated,
mainly because of light pollution problems in Crimea. Besides variable-star
fields, a significant part of the series are photographs of galactic globular
clusters (with a typical exposure of 30 minutes, or less, down to ~5 minutes
in special cases, like studies of bright Cepheids near cluster centers).
Fig. 1. The yearly numbers of plates
taken with the Sternberg Institute's 40~cm astrograph.
For decades, the plates from the 40-cm astrograph were extensively
used for variable-star research. Nevertheless, the plates still contain a lot
of valuable unused scientific information. As an example of scientific
treasures waiting to be evaluated for many years, we would like to mention
the discovery of the supernova SN 1983ab, visible on 24 plates, by Antipin in
1996 [2, 3].
Also of considerable importance are direct and objective-prism
plates taken in the prime focus of the 50-cm Maksutov camera in Crimea. There are also many
rich variable-star centers of direct plates in this series, as well as
photographs of star clusters and associations. Most direct plates and films
from the Maksutov telescope were taken behind filters, in the bands of the UBVR system. The exposure times were
from one minute to several hours. An interesting subset of this series are
direct plates of the local-group galaxies M 31 (the Andromeda nebula) and
M 33 (the Triangulum nebula), taken mainly for discoveries and studies
of Novae in these galaxies. This observing project was initiated by Prof.
A.S. Sharov before 1970. We have 1853 Maksutov-camera plates of M 31 plus 60
plates of this galaxy taken with the Schmidt telescope at Baldone, Latvia
(many more M 31 plates from the Schmidt telescope are kept in the Baldone
collection proper) and some 20~plates from other telescopes, including
Bulgarian instruments. Our plates of M 31 cover the time interval between
1968 and 2004. These plates of M~31 were used to discover 65 Novae in M 31,
to confirm (or not confirm) a number of Novae discovered elsewhere (see, for
example, [4]). Currently the project is continued by A. Alksnis (Baldone) and
A.~Zharova (Moscow). For M 33, the time interval is 1973–-2004; we have 844 Maksutov
plates and 164 plates from the 40-cm astrograph. For the photographs of the
galaxies M 31 and M 33, we have the catalog of plates ready in the electronic
form.
The quality of the direct plates taken with the Moscow 70-cm
Cassegrain reflector (also behind filters, UBVRI) strongly depends on seeing. On poor-seeing nights,
individual variable stars were photographed. Excellent-seeing nights were
used to study star clusters and variable stars in close double systems,
taking advantage of the telescope's large focal length and of the
corresponding scale (about 18'' per mm).
3 The Zvenigorod
Plate Collection
Besides the Sternberg Institute plate
collection, there also exists a plate collection at the Zvenigorod
Observatory of the Institute of Astronomy (Russian Academy of Sciences). The plates kept there were taken after 1972 with
the Observatory's 40-cm Carl Zeiss astrograph (F=200 cm, field size 8o×8o, limiting
magnitude down to 18m on the best plates). The telescope is
similar to the GB astrograph of the Sonneberg Observatory. The Zvenigorod
plate collection contains about 4500 plates (sky fields of a special-purpose
photographic sky survey, asteroids, comets, Pluto, fields of optically
identified radio sources). Slightly less than 100 plates from the same
telescope, taken for variable-star studies, are contained in the Sternberg
Institute's plate collection. There are also some 15000 sky photographs on
films in Zvenigorod, taken with a very wide angle (10×150 degrees)
satellite-tracking camera.
4 Digitization
Projects in Moscow and Zvenigorod
The necessity
to digitize our plate collections was correctly understood several years ago.
We used the opportunities to learn about the experience gained in the
digitizing projects of the Maria Mitchell Observatory (USA), of Italian
astronomical institutions, and of the Sonneberg Observatory, made use of
digitized plates from foreign observatories in our work (see, for example,
[5]).
In December 2004, the Sternberg Institute acquired two CREO Ever
Smart Supreme flatbed scanners (Fig. 2) and launched the digitization
project. These scanners are very expensive, and their acquisition became
possible thanks to special funds provided on the occasion of the 250th
anniversary of Moscow University. The scanning area can be as large as 305×432 mm, with the
optical resolution up to 5600 dpi. The maximal density is 4.3D. As an operating computer, the
scanners require Apple PowerMac G5.
The scanners were installed in an
air-conditioned room with stabilized electricity and access to Internet.
Currently, we are acquiring equipment for data storage and processing.
Extensive experiments have been undertaken in order to select the best
scanning mode for our purposes. These experiments are close to their
conclusion, and we are planning to start large-scale
scanning in the second half of 2005.
Fig. 2. One of the CREO scanners at the
air-conditioned scanner laboratory of the Sternberg Institute.
Earlier in
2004, the Institute of Astronomy purchased two semi-professional Epson Expression 1640~XL
scanners. For them, the maximal size of transparent originals is
290×420 mm. The optical resolution is 1600 dpi; in our opinion, such a
resolution is insufficient for best-quality direct plates, but it is good
enough for many kinds of scanning works in our plate collections. The maximal
density is 3.6 D. It is important
that the same scanner system is in use in plate collections of several
European countries (see contributions in this volume). Such scanners are much
cheaper than the CREO scanners, they require Windows PCs, a much more
frequently-met computer type at our observatories. Initially, one of the
Epson scanners was installed at the Sternberg Institute, but now, with the
two CREO scanners working there, both Epson scanners are located at the
Zvenigorod Observatory.
The scanning team of the Zvenigorod Observatory maintains a web
site (http://skanlab.narod.ru) containing technical information and providing
access to low-resolution previews of some scanned plates. So far, the
language of this web site is mainly Russian.
The two scanning teams work in a close cooperation. We compare
scanning results, jointly discuss scanning modes to be used. It is understood
that the most historically and scientifically valuable parts of the Sternberg
Institute's plate collection will be scanned with the CREO scanners, at the
2540~dpi resolution, whereas the Zvenigorod plate archive and some less
important plates of the Moscow collection will be scanned with the Epson
scanners.
Acknowledgments
We are
grateful to the organizers for inviting our team to the conference and for
possibility of presentation of our projects. Our scanning project is
supported, in part, by the Russian Foundation for Basic Research (grants 05-02-16289, 05-02-16688) and by the
Program of Support to Leading Scientific Schools of Russia
(grant NSh-389-2003-2). Thanks are due to Dr. S. Antipin for his assistance
during the preparation of the manuscript.
References
1. S.
Shugarov, S. Antipin, N. Samus, and T. Danilkina (1999) Acta
Historica Astronomiae 6 81.
2. N. Samus and S.V. Antipin (1996) IAU Circular No. 6439.
3. S.V. Antipin (1996) Comm. 27 and 42 IAU Inform. Bull. Var.
Stars No. 4361.
4. A.S. Sharov, A. Alksnis, A.V. Zharova,
and Yu.A. Shokin (2000) Astronomy
Letters 26 433.
5. P. Kroll,
N. Samus, and I. Volkov (2003) Comm. 27 and
42 IAU Inform. Bull. Var. Stars No. 5441.
