Some useful astronomical links
The Digital Sky Survey
As part of the activities leading to the Guide Star Catalog (GSC) photographic plates
covering the whole sky where scanned. For the northern hemisphere, a new set of
shorter exposure plates (the Quick-V plates) were obtained. For the south the
ESO/SERC Southern J plates were used. In addition some regions were covered by
special plates. In parallel with the scanning, the original Palomar Observatory
Sky Survey (POSS-I) XE plates were scanned. The latter and the southern plates
constitute the Digitized Sky
Survey (DSS). A detailed description of the GSC, its contents and the
plates used can be found in Lasker et al. (1990),
Russell et al. (1990)
and Jenkner et al. (1990).
Once these scans were finished the two PDS
machines at STScI were completely refurbished. After an agreement with the
Palomar Observatory, the plates that constitute the POSS-II are being scanned.
All these scans are available on-line (http://archive.stsci.edu/dss/).
original scans were made with a pixel size of 25µ, resulting in a 14,000 x
14,000 pixel image with a scale of 1.67"/pix. A 512x512 image covered then an
area of 14.3'x14.3'. The new scans are done with a pixel size of just 15µ
resulting in a raster of 23,000x23,000 pixels.
Please note that to provide
coordinates for targets to be observed with the Hubble Space Telescope it is
necessary to use only the plates used to create the GSC and not the ones
from the POSS-I.
The Digitized Sky Survey is a set of CD-ROMs containing the
POSS-I XE and SERC J scanned plates compressed 10X. It covers the whole sky. A
100X compressed version, called RealSky is presently available only for the
northern sky, with the southern part to be released soon. Both sets are sold by
the Astronomical Society of the Pacific.
These new scans will be used to
construct the GSC-II. This updated version will include 2 x109 objects (100
times more than GSC-I), at least 2 epochs and 2 bands; proper motions will be
calculated with an error less than 4.0 mas/yr and a magnitude error between 0.1
and 0.2mag (GSC-I did not contain proper motion information and the magnitude
error is 0.4mag).
Automatic Plate Scanner
The University of
Minnesota created the Automatic Plate Scanner
Catalog (APS) from the scans of the POSS-I O and E plates with |b| > 20o.
The catalog consists of a list of classified objects found on both plates using
a neural network algorithm to separate the stellar and non-stellar objects. The
two catalogs (one for each band) are available on-line (http://aps.umn.edu),
they contain coordinates, magnitudes, colors and other parameters. They
provides information on 108 stars and around 107 galaxies up to a limiting
magnitude of less than 21 in the blue.
The Institute of Astronomy of the Bulgarian
Academy of Sciences maintains a database of
Wide-Field Plates (http://www.wfpa.acad.bg). The information is standardize
and lists the object name, emulsion and filter, J2000 coordinates and UT.