1. VII BSAC  "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
Wide field plates observations of stars from Earth Orientation Catalogs (EOC)
Yavor Chapanov1, Katya Tsvetkova2, Milcho Tsvetkov2,
Jan Vondrák3, Cyril Ron3, Vojtéch Štefka3
1 – Central Laboratory for Geodesy, Bulgarian Academy of Sciences
2 – Astronomical Institute, Bulgarian Academy of Sciences
3 – Astronomical Institute, Academy of Sciences of Czech Republic

2. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
DATA SOURCE
EARTH ORIENTATION CATALOGUE EOC-4
objects, determined from
4.5 million observations of
latitude/universal time
WIDE-FIELD PLATE DATABASE WFPDB
- Catalogues of Wide-Field Plates with
more than entries

3. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
EARTH ORIENTATION CATALOGUE EOC-4

4. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
EARTH ORIENTATION CATALOGUE EOC-4
DECLINATION EPOCHS
- significant number of stars with
mean epochs before 1990
- long observational series

5. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
EARTH ORIENTATION CATALOGUE EOC-4
RA EPOCHS
- small number of stars with
mean epochs between 1975 and 1990
- short observational series

6. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
EARTH ORIENTATION CATALOGUE EOC-4
Proper motion in declination
- stars with pmDE>0.05”/a are
potential source of systematics

7. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
EARTH ORIENTATION CATALOGUE EOC-4
Proper motion in RA
- stars with pmRA>0.05”/a are
potential source of systematics

8. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
EARTH ORIENTATION CATALOGUE EOC-4
Parallax
- non-linear proper motion is more
visible for stars with greater parallax

9. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
EARTH ORIENTATION CATALOGUE EOC-4
STAR MAGNITUDE
- between 0 and 12
mean magnitude 6.5
- significant number of bright stars
star images cover more pixels
- better accuracy

10. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
WFPDB – Telescopes and plates
VIEW ANGLE [degree]
- 1, 3, 5, 7, 20, …
APERTURE [cm]
- 10, 12, 14, 16, 34, 40, 60, 67, …
PLATE SCALE ["/mm]
- 830, 295, 860, 258, 300, 102, 115, 96, …
SCAN RESOLUTION [dpi]
- 300, 600, 1200, 2400, 4800, 9600, …

11. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
WFPDB – Star position accuracy
ACCORDING PLATE SCALE (emulsion corn 10m)
100"/mm - ±0.5"
60"/mm - ±0.3"
13"/mm - ±0.06" (Rozhen)
ACCORDING SCAN RESOLUTION
300dpi=12d/mm+scale 13”/mm ±0.5"
600dpi=24d/mm+scale 13”/mm ±0.3"
1200dpi=47d/mm+scale 60"/mm ±0.6"
2400dpi=94d/mm+scale 100"/mm - ±0.5"
4800dpi=189d/mm+scale 100"/mm – (±0.3“)
9600dpi=378d/mm+scale 100"/mm – (±0.1“)

12. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
WFPDB – Plates: position accuracy
PLATE CENTER
- current accuracy (1”,1”), necessary (0.1”, 0.1”),
determined by 7-parameter transformation
PLATE ORIENTATION
- determined by 7-parameter transformation
ANGULAR DISTANCE FROM THE CENTER
- max 5°

13. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
WFPDB – Plates: Access
FREE ACCESS
- compressed images
SCAN RESOLUTION
- as high, as possible (interpolation)
SEARCH
- by the scale parameter (<100”/mm)
TOOLS
- 7-parameter transformation (plate center)
- distortion model improving
- star identification and coordinates extraction

14. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
CONCLUSIONS
The WFPDB provide significant number of plates, containing a given star. The observation epochs cover century time span, which is useful to improve star catalogs.
It is necessary to improve the free access to the digitized plates and to add some new options in the search engine and tools:
- improve resolution to 4800dpi or more and compress the images
- search for plates with scale <100arcsec/mm
- online tool for identification of a group of stars from a given plate sequence
- accurate determination of the plate centers and their orientation by 7-parameter transformation

15. VII BSAC "ASTROINFORMATICS" – Chepelare, 1-4 June 2010
THANK YOU
FOR ATTENTION