Transcript AC/CdC report IAU GA Sydney

AC/CdC WG Report
Sean E. Urban
U.S. Naval Observatory, Washington DC
IAU GA XXV Sydney
Website
• Much of the WG activities & info on AC/CdC found at:
http://astro.u-strasbg.fr/~fresneau/workgroup.html
IAU GA XXV Sydney
Working Group Members
Carlos Abad
Robert Argyle
James Biggs
Noah Brosch
B. Bucciarelli
G. Coyne
E. Davoust
J.P. De Cuyper
E. van Dessel
C. Ducourant
I. Bustos Fierro
M. Geffert
E. Glushkova
M. Irwin
D. Jones
K. Kuimov
A. Kuzmin
Chen Li
K. Lumme
J.L. Muinos
M. Odenkirchen
R. Orellana
T. Pauwels
T. Rafferty
M. Sanchez
J. Sanner
M. Tsvetkov
S. Urban
A. Vaughan
A. Fresneau (Chair)
IAU GA XXV Sydney
Brief Overview
• Astrographic Catalogue (AC)
– All stars to b=11.0; Ep. ~1907
– Over 22,000 plates; 2x2 degrees; 2-fold overlap; scale=60”/mm
– Multi-institutional, forerunner of IAU
• Carte du Ciel (CdC)
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All stars to b=14.5; Ep. ~1912
Same instrument as AC; same 2x2 deg plates; same overlap, scale
Goal: odd zones w/ 1 exp.; even zones w/ 3 exposures
Paper charts to be made w/ even zone plates
~7500 plates
IAU GA XXV Sydney
Valuable data?
• AC
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Plates measured by hand; published; keypunched
Data reduced (AC 2000.2); used in Tycho-2, UCAC2
Errors ~200 to 400 mas/image
Some improvement gained in re-measurment; worthwhile?
Currently available for future use
• CdC
– Most plates never measured
– At 200 mas, p.m. ~2 mas/yr
– Better than anything currently available
IAU GA XXV Sydney
Example of CdC plate
IAU GA XXV Sydney
Programs in Progress
• Bordeaux zone (+11 to +17)
– 500 plates w/ APM (Cambridge); combined w/ current epoch TC data
• Sydney (-65 to –51)
– 500 plates w/ APM (Cambridge);
• San Fernando (-10 to –2)
– 400 plates w/ scanned, available on CD
• Toulouse (+4 to +10)
– Rapid scanner in search of lp variables
• Cordoba/Uccle
– Testing measuring machines
IAU GA XXV Sydney
Results
IAU GA XXV Sydney
Results
From Sydney and Bordeaux CdC
• Positional errors:
– 120 to 180 mas “internal”
– 150 to 300 mas global
• Photometric errors:
– 0.1 mag internal
• Variablity of stars on short periods detected and believed real
– 0.35 mag external
• Plates aging:
– Degradation in reaching faintest stars
IAU GA XXV Sydney
Discussion
• Plates currently in jeopardy; age, apathy
• Who to save plates/digitize images?
– Sub-micron measuring not needed (“fast scanners?)
– Identify unique set of plates to test machines?
– Archive raw images or only save (x,y)s?
• Keep the WG active in Comm 8?
• Join the Preservation and Digitization of Photographic Plate
WG?
IAU GA XXV Sydney