Transcript 4. Database of FITS images of extragalactic radiosources

Bucharest Plates and CCD
Database
Petre Popescu, Gheorghe Bocsa,
Alin Nedelcu, Liviu Serbanescu, Octavian
Badescu
Astronomical Institute of Romanian Academy
5 Cutitul de Argint street, Bucharest, Romania
www:astro.ro
1. Introduction
Within the Wide-Field Plate Archive program initiated by IAU
Commission 9,
• 2260 plates were archived in the period 1930 – 1951 at Bucharest
Observatory – under the aegis of University;
• 10729 plates were exposed from 1952 until now, when the
Observatory was affiliated to the Institute of Atomic Physics and the
Romanian Academy.
The observations were performed in the zone – 200<δ<+700 (English
mounting) with a Prin Merz refractor (f=6m, d=38cm) and Zeiss
Canon camera (f=80cm, d=16cm). The refractor field is up to 20×20
(1mm=30’’) and that of Zeiss Canon camera is 70×100 (1mm=4’).
Zeiss camera was used only for the exposure of 180 photographic
plates of 13×18cm.
2. Qualitative study of the plates observed with
Bucharest astrograph
The observational program had
• 3 maxima: 1930-1940, 1952-1977 and 1980-1998;
• 3 minima: Second World War, 1977 Earthquake (the dome was
damaged), 1998 - deteriorated astroclimatic conditions.
In the first period, observations were made for asteroids, as well as
for some great planets, comets and lunar eclipses. In spite of the long
time elapsed most plates have preserved a good aspect. While
finalizing the “previews” for the first group of 2260 plates, we have
noticed that the content of many plates is not the expected one
because the observers’ lack of professionalism and collaboration. In
that time, the Observatory didn’t issue any publication, processing
was difficult and lacked calculations means, (besides we suspect) that
few processing were sent to Rechen Institute in Berlin. There were
performed observations in the hope that in the future processing
might also be performed.
2. Qualitative study of the plates observed with
Bucharest astrograph
• In the first period, good plates with adequate exposure is a
valuable source of asteroids and comets positions they indicate
the orbits of that bodies.
• An activity acknowledged worldwide was the observation of
Jupiter’s Galilean satellites by prof. Gh. Petrescu, who built a
mechanic device by means of which he was able to photograph
with adequate exposure times the reference stars, satellites: Io,
Europe, Ganymede, Callisto and Jupiter! His work made up a
doctorate thesis which was defended at Paris Observatory – all
data being published, also where we suspect that the plates are.
The observations were resumed in the period 1982-1985 and
new results were published.
2. Qualitative study of the plates observed with
Bucharest astrograph
• A special event was the discovery in the archive of a number of
plates with Pluto, observed by the academician Gh. Demetrescu
in January 1932, together with other observations performed in
1975 by Cornelia Cristescu – processed with respect to the
epoch J2000.
• In 2001 the paper “Observations of Pluto in Bucharest during
1932 and 1967-1975 ” was published, data processing being
made for the epoch J2000.
• In the plate archive we have found several high quality plates
with Daimaca comet from September 1943.
2. Qualitative study of the plates observed with
Bucharest astrograph
• The second period brought the acknowledgement of
photographic astrometry working group.
- There were performed comet and asteroid observations to
improve their orbits, the data were finalized in Smithonian
Astronomical Observatory;
- Observations of great planets: Jupiter, Neptune and Pluto;
- Photographic determinations of the orbits of Galilean
Satellites of Jupiter – Petrescu (1935, 1938, 1939) and Bocsa
(1994);
- In 2009 Neptune will make the first complete rotation around
the Sun since its discovery by Le Verrier and Adams in 1846.
The paper “Observations of Neptune in Bucharest Observatory
during 2001-2004” was published in Romanian Astronomical
Journal to this effect.
2. Qualitative study of the plates observed with
Bucharest astrograph
• Because in that period was no telescope in Bucharest, we use the
astrograph for observations of stellar clusters (24 plates), double stars
(81 plates) and variable stars (105 plates).
Within the framework of this program was observed the Pleiades
region for the period 1955-1958. It was possible to use them for the
project investigation of the long variability of the Pleiades red dwarf
stars, together with Byurakan, Konkoly, Rozhen, Postdam and
Sonnenberg Observatories. There are more than 80 plates, which
might be object of future usage of the archived observations due to
the long period time coverage.
2. Qualitative study of the plates observed with
Bucharest astrograph
Great programs collaboration in the field of photographic astrometry:
• Between 1957 – 2000 we participated in the program initiated by
Rechen Institute Heidelberg and Institute of Theoretical Astronomy
Leningrad for observations of a designated number of asteroids, as
well as for the determination of an inertial system of stellar reference.
• Within “Stellar proper motions” program with Pulkovo Observatory,
at the first stage (1957 – 1965) we used 151 galaxies and 275
fundamental stars as fixed reference points for the determination of
stellar proper motions, zone - 200<δ<+700.
At the second stage (1980 – 1990), faint distant stars were used.
During this stage, because of the deterioration of the astroclimatic
conditions in Bucharest, only stellar areas with 14m were used, in the
zone - 200<δ<00.
2. Qualitative study of the plates observed with Bucharest
astrograph
• The program “CONFOR” (started in 1992) has as aim to make the
connection between radio and optical reference frames.
In the first step, we observed 188 stellar areas with a declination
range of - 200<δ<+700 (finalized in 2000).
In the second step (which is in work now) we use CCD techniques to
observe the radio-sources and the reference system around them.
This step is performed in Belogradchik Observatory using a 60cm
Zeiss reflector (see part 4).
• ESA program “COROT” envisages the observational analyze of two
zones, by comparing old photographic plates with new exposed
plates, for the evaluation of the dynamics of this two stars in the
Galaxy. For the first star we found a pair plate of 13×18cm in the
year 1939. For the second in WFPDB we found in Sonnenberg
Observatory a plate observed in 1950 (6h 48m, -00 30m).
2. Qualitative study of the plates observed with
Bucharest astrograph
• Occasionally observations of phenomena as: total or partial solar
eclipses, Regulus occultation by Venus (1959), Mercury transits
across solar disk (1970, 1973).
• Photographic material is still in good shape due to the good
preservation conditions in the plate archive. There are several plates
which have not been washed properly, but when the previews will be
done, they will be reconditioned.
The plates 13×18cm, made with Zeiss camera are underexposed and
for many plates from the first stage (1930 – 1951) the observational
subjects cannot be found in the images obtained.
The content of the plates after 1980 is good, but because sky
conditions they are darker and increasingly difficult to process.
Till now we have 2300 preview plates (1930 – 1951), in the end of
2008 we will have 10000 preview plates (1930 – 1980).
3. Plate information recovery and analyse
In the digitized information from the plates archive may
occur errors caused by several factors as:
- physical degradation of the plates,
- the digitization process (from scanning, photographing, etc.),
- measurement processes (to obtain the coordinates for certain
celestial objects that are on that plate), etc.
3. Plate information recovery and analyse
Comparing common areas with similar measuring methods, it is
possible to determine models for the distribution of the errors (for
errors that may occur during digitization process, respectively the
measurement process) or evolution models of the errors (in the case
of degradation of the plates).
These models may be used to compensate the occurring errors or to
delimit them. In a digitized database the comparing operations for
common areas may be done automatically by the software. It will be
obtained the determination of the identical areas from star catalogs
with minimal tolerance from the measurement's and classification's
point of view, having as result fuzzy models for the occurring errors.
Using these fuzzy models the digitized plates library may give
information regarding the level of "trust" level of each digitized
image.
3. Plate information recovery and analyse
• Clasification of the errors
The errors that occur, from the digitized information of the plate
archive, can be divided in errors that do not change in time –
static errors – and errors that change in time – dynamic errors.
- A. Dynamic errors - due to physical degradation of the plates
(mainly defect of the photographic emulsion with evolution in
time, materialized by the change of magnitude on the plates);
- B. Static errors - measuring errors caused by:
- B.1. Equipments used for digitization;
- B.2. Methods or softwares used during the measuring
process;
- B3. Other causes – difficult to be quantified (results of the
photographing process, initial defects of plates, etc).
3. Plate information recovery and analyse
•
Error's detection and model’s construction
1. Error's detection by software (in a database which contains
digitized plates)
It is possible to make a software application which analyze data
in a databases (with digitized plates) and to determine the
common areas (areas that will be found in more then one
digitized plate - from same or different observatories).
These detected areas by the software are entering in the error's
analysis process. Based on information that are corresponding
to selected digitized plates it can be built fuzzy models.
In this models may enter, effectively, all associated information
of the digitized plates.
3. Plate information recovery and analyse
• Error's detection and models construction
2. Error's detection by experiments (Realized on samples
chosen after series of classification in plate archive)
A. To put in evidence the resulted errors from time degradation
of plates may be done by successive digitization of same plate.
It can be performed at few months interval and making
measurements for the references of the plate in the same
conditions. From deviations, will be build an evolution model
in time. Applying regression techniques we will determine the
mathematical model. The model will be in one of the following
form:
Ym = Fm(p,m,t)
where Ym represents the deviation of the magnitude,
p - depends of the type of the plate,
m - depends of the measurement method,
t - is the time (the number of months)
3. Plate information recovery and analyse
• Error's detection and models construction
2. Error's detection by experiments (Realized on samples
chosen after series of classification in plate archive)
B.1. The errors that are generated by the models or by the
software used in the measuring process.
The measurement may be evidenced measuring the reference
celestial object position for the same digitized plate using
different methods and software.
3. Plate information recovery and analyse
The models will have the following form:
Ys = Fs(m,r,i,p,s) Yu = Fu(m,r,i,p,s) Ya = Fa(m,r,i,p,s)
where Ys represents the deviation from the magnitude,
Yu represents the angle where the deviation appeared,
Ya represents the absolute value of the position's deviation,
s represents the type of the scanner,
r represents the the scanning resolution,
i represents the pixel from the image
p - depends on the type of plate
m - depends on the measurement method,
The model will be a fuzzy model.
3. Plate information recovery and analyse
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B.2. The errors due of the used equipments for digitization, may be put into
evidence digitizing same plates with different equipments, using the same
measuring methods to determine the position of the reference celestial objects.
The models would have the following forms:
Ys = Gs(s,r,i,p,m)
Yu = Gu(s,r,i,p,m)
Ya = Ga(s,r,i,p,m) ,
where Ys represents the deviation from the magnitude,
Yu represents the angle where the deviation appeared,
Ya represents the absolute value of the position's deviation,
m is a measure that depends by the measuring method and the
measuring software,
s represents the type of the scanner,
r represents the the scanning resolution,
i represents the pixel from the image
p is a measure that depends on the type of plate.
The model will be a fuzzy model.
The software may replace the experimental test to detect and create models
for digitized plates if the digitized plates archive already exists.
3. Plate information recovery and analyse
A. The errors models obtained by analyze of dynamic errors
(degradation in time of the plates) is useful for:
- setting the priorities regarding plates scanning;
- for some plates, the old ones, may improve the measurements (the
corrections applied based on the model will bring the digitized image
closer to the initial one).
B. Models resulted from the analyze of static errors may be used for
the improvement of the quality of the measurement techniques as
well as for choosing the optimal equipments for digitization.
- The first benefit of the database brought by the software is linked to
the “trust level” that may be attached to each plate that contains
common areas with other plates that exist in the digitized plates
archive.
- In addition, the software will offer errors’ analyzing models
corresponding to the plates.
4. Database of FITS images of extragalactic radiosources
•Astronomers are able to share data (images, spectra), because they share
a common data description called FITS (Flexible Image Transport
System).
•The FITS rules are endorsed by the International Astronomical Union,
and codified into a formal standard by the NASA/Science Office of
Standards and Technology.
•The FITS standards make observations from any instrument usable by
any astronomer, and many generic tools for data visualisation and
transformation have been developed.
•Various programming libraries provide the infrastructure of the
input/output high level function needed to access the FITS data – QFITS
(ESO), CFITSIO (NASA)
4. Database of FITS images of extragalactic
radiosources
The CCD images of the extragalactic radiosources observed so far are
stored on DVDs.
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The total amount of data is 26 GB including the science and calibration
images.
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For an easy access to these images obtained in the last 3 years the FITS
structure is stored in a MySQL database

An web interface based on PHP provides a reasonably flexible way to
query the database
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A more powerfull way to access the database is to use SQL queries in
stand-alone C programs running in batch mode
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4. Database of FITS images of extragalactic
radiosources
•The database is updated in remote mode after every observational run;
•A stand alone C program using CFITSIO library to access the FITS file
and MySQLCLIENT library to communicate with the database is parsing
the folder of the last observations;
•FITS headers togheter with the actual path of each image are stored in
the MySQL database;
•SQL query example: find all the regions observed at a given date (JD):
SELECT RA, DEC from DATABASE where TJD >JD -1 AND TJD < JD
+ 1.
5. Conclusion
•Reusing the data from older projects (photographic plates) for new
scientific objectives is also necessary to optimise their scientific return
(asteroids recovery and/or discoveries);
•The need to uniformally describe the heterogenous data (tables, images),
or data of similar types but obtained on different arhitectures
(photographic plates, CCD images);
•The perspective of a European regional storage center and a colaborative
data-mining project;
•New methods, tools, and techniques for the preparation and use of the
existing data.