Sub-group on the Densification of the Optical Frame
Newsletter 3
February 8, 1999
Dear Colleagues,
This is the third newsletter of the Sub-group on the Densification
of the Optical Reference Frame. Several projects have been progressing;
updates are given below. The projects which I have received information
from are the Southern Proper Motions Catalog, USNO CCD
Astrograph Catalog, Tycho-2 Catalogue, work at the Shanghai Astronomical
Observatory, and the FAME Astrometric Satellite. Note that under the
Shanghai Astronomical Observatory news is a call for collaboration.
I have yet to hear any complaints about the website, therefore I am
assuming that all can read it. I will continue to add information to
it and use it as my primary source of disseminating information.
Sincerely,
Sean Urban
U.S. Naval Observatory
February 8, 1999
http://aries.usno.navy.mil/ad/dens_wg/dens.html
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Southern Proper Motions Catalog (from Platias and Van Altena)
Dear Colleagues,
On behalf of the Yale Astrometry Team we announce availability of the
second installment of the SPM catalog. The SPM Catalog 2.0 provides positions,
absolute proper motions, and photographic BV photometry for over 320,000
stars and galaxies. All objects contained in the SPM 1.0 Catalog
(the South Galactic Pole region) are also included in this version.
Note that SPM 1.0 has been replaced by SPM 1.1 which has slightly
different astrometry (mostly proper motions) due to refinement of the
magnitude equation correction in the SPM 2.0 Catalog.
The Catalog covers an area of ~3700 square degrees in an irregularly
bounded band between declinations of -43 and -22 degrees, but excluding
fields in the plane of the Milky Way. Stars cover the magnitude range
5 < V < 18.5. The standard errors for the best measured stars are as follows:
20 mas for positions in each coordinate; 2 mas/yr for absolute proper motions
and 0.05 mag in B and V bandpasses. In addition to the Catalog, a list of
CCD calibrating sequences in BV is provided. It contains 7783 stars. The new
feature of the Catalog is an extensive list of cross-identifications with
external special catalogs which include all major astrometric catalogs and
a large number of astrophysically interesting objects.
The Catalog is available on the WWW at http://www.astro.yale.edu/astrom/
Our web-site contains several useful plots showing the sky coverage, error
distribution, a quick comparison with the Hipparcos proper motions, etc.
We would appreciate your comments on the SPM 2.0 and our Web page.
Sincerely,
Imants Platais,
Bill van Altena
(Yale University)
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USNO CCD Astrograph Catalog (from Norbert Zacharias)
The US Naval Observatory Astrograph Catalog South (UCAC-S) project
is proceeding very well. Started in January 1998, over 40% of the
Southern survey was completed by the end of 1998. Preliminary
reductions indicate that all target parameters can be met
(approx 20 mas positional accuracy). Over 50,000 frames
have been taken starting at the South Pole. It is planned to
produce and release a 1-year catalog in 1999, likely covering a
complete section of the sky with declinations south of approximately
-38 degree.
UCAC-S data together with CTIO 0.9-meter observations provided the
link of the Hubble Deep Field South to the Hipparcos system. The
accuracy of this link is believed to be on the 30 mas level for
stars down to 21th magnitude. (See AAS meeting 193 poster paper)
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Tycho-2 Catalogue (from Erik Hoeg)
The Tycho-2 Catalogue of about 2.5 million stars:
Positions, proper motions, B_T and V_T magnitudes.
Expected release: End of 1999.
A new reduction of the original Tycho photon counts obtained with
the ESA Hipparcos satellite has been carried out. This has
improved the astrometric and photometric precision of the fainter
part of the one million stars in the Tycho Catalogue, and increased
the total number of stars to about 2.5 million. The original
Tycho reduction was done by detecting a significant signal
whenever the stars of an input catalogue crossed a slit system
in the focal plane of the Hipparcos telescope. The improvement
in the new reduction was achieved by making a superposition of
the photons that were counted during all the about 130 observations
per star obtained during the mission. The proper motions will be
derived from positions in the AC and 160 other catalogues.
A paper containing details of the Tycho-2 project can be found at
http://www.astro.ku.dk/~erik/papers/tycho2.ps.gz
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News from Shanghai Observatory (from Shuhe Wang)
The positions and absolute proper motions of 534 stars near the
central region of the globular cluster M31 about 1.5 deg*1.5 deg
area were determined with 14 plates in two epochs taken with 40
cm refractor at Sheshan station of Shanghai Observatory. The
central overlapping method and 24 stars of the ACT catalogue as
reference frame were used in the reduction. The absolute proper
motions of this globular cluster are -0.3(+/-)0.3 mas/yr in right
ascension and -3.1(+/-)0.3 mas/yr in declination. Meanwhile the
probability of membership was estimated with these proper motion.
( Author: Zhenyu WU, Jiaji WANG)
Using ACT Reference Catalogue as a preliminary reference
catalogue, we have reduced 31 exposures on 15 plates in two sky
areas taken with the 40cm refractor at SheShan Station of
Shanghai Astronomical Observatory. By means of the central
overlapping technique and the iterative process, highly precise
positions and proper motions of 54 stars, including 16 Hipparcos
stars in the two sky areas are obtained. The mean values of the
internal standard errors of proper motions in right ascension and
declination for 16 Hipparcos stars are 0.70 mas/yr and 0.59
mas/yr, respectively. The mean values of the internal standard
errors of their positions are 10.5 mas and 7.5 mas in two
position directions,respectively. (Author: Shuhe WANG, Zhenghong
TANG, Wenjing JIN)
Around the extra-galactic radio source 0316+413, the positions,
proper motions, and magnitudes of 177 stars were determined with 7
plates, with the same method and reference catalogue as mentioned
above. (Author: Zhenghong TANG, Shuhe WANG, Wenjing JIN)
Call for collaboration:
We are performing a program with the purpose to get absolute
proper motions of about 1000 Hipparcos stars with the precisions
better than 1mas/yr, half of them will be accessible to
0.5mas/yr; at the same time, to densify the stars down to 15.0
mag in the some sky areas using photographic plates with large
epoch differences of the 40cm refractor (f=6895mm) at SheShan
station of Shanghai Astronomical Observatory. The telescope has
been used for more than ninety years since 1901, about 3500
plates were photographed. The statistical results for some plates
showed that the optical and mechanical systems of the telescope
are still stable now. The plate size is generally about 30cm*24cm
(2.5 deg *2 deg). Our program will use these plates covering the
same sky region and having large epoch differences (up to 90
years) to improve proper motions of about 1000 Hipparcos stars
and densify the stars down to 15.0 mag.
The database about the plates such as: observational date,
exposure time, positions of the plate center(R.A.,Dec.) and so on
have been constructed (CDS Bulletin No.49). Now we are facing two
difficulties, the first is all plates had been used before 1995,
we cannot get more observations, and we cannot buy new plates
because the factory is not willing to produce the special size
plates with small number. The second difficulty is that the PDS
system we used before is not stable when it scans the whole
plate. To solve the two difficulties mentioned above and finish
the program better, we need collaboration with anyone who is
interested in the program.
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FAME Astrometric Satellite (from Sean Urban)
On January 25, 1999 NASA announced that 5 missions out of 35 submitted
proposals have been selected for MIDEX Phase A study. FAME was
one of the five. The five were selected primarily on scientific
value. The four month long Phase A study will emphasize project
management, costing and technical feasibility. Two of the five
missions will be selected for full funding. That selection should
take place in September, 1999. For additional details, see
http://www.usno.navy.mil/fame.
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