Techniques
of Observational AstronomyAST3722C
Techniques
of Observational AstronomyOur information on astronomical objects has traditionally been kept primarily in the form of catalogs (usually a printed list of objects and selected characteristics) and atlases (maps of the sky). More recently, computerized databases have become the dominant source of information.
The primary use of these resources is
Whether traditional (hard copy) or modern (computerized), usually a variety of resources are required to accomplish any one task.
The Bright Star Catalogue (variously called the BSC, YBSC, YBS etc.) was widely used as a source of basic astronomical and astrophysical data for stars brighter than magnitude 6.5. 9096 of the catalogued 9110 objects are stars, while 14 were subsequently found to be either novae or extragalactic objects. These 14 have been retained to preserve the numbering. For the 9096 stars, the BSC provides identifications in several other widely-used catalogs (including double- and multiple-star identifications), equatorial (B1900.0 and J2000.0) and galactic coordinates, proper motions (J2000.0), UBVRI photoelectric photometric data (when they exist), Morgan-Keenan (MK) spectral types, and a wide range of other useful information. Star names of the form BSnnnn or HRnnnn (from Harvard Revised) will be references to this catalog.
The last printed version was "The Bright Star Catalogue; 4th revised edition, by Dorrit Hoffleit with the collaboration of Carlos Jaschek, 1982". A Fifth edition isavailable only in machine readable form and may be found at http://xml.gsfc.nasa.gov/archive/catalogs/5/5050/index.html. Most Planetarium software packages include versions of the YBSC as part of their database.
The BD is a visual survey of stars in the declination zones +89 to -01 degrees. The survey, completed by Argelander and his assistants in the years 1852-1861, was performed and the stars cataloged by allowing the telescope to drift along the mean declination of each zone and recording the positions and magnitudes of stars crosssing the transit line of each field. The goal of the survey was to obtain a position and estimated visual magnitude for every star visible with the 78-mm Bonn telescope. Actual magnitude estimates were recorded to 0.1 mag for all stars down to 9.5 mag, with fainter stars being assigned to 9.5. Thus, the BD actually contains a rather large number of stars fainter than 10.0 mag. Positions are given to the nearest 0.1 sec in Right Ascension and 0.1 arcmin in Declination.
The Cordoba Durchmusterung is a visual survey of southern stars in declination zones -22 to -89 degrees (equinox 1875), carried out as an extension to the Bonner Durchmusterung. The survey was performed using techniques similar to those used for the BD, i.e., the stars were cataloged by allowing the telescope to drift along the mean declination of each zone and recording the positions and magnitudes of stars crossing the transit line of the field. The goal of the survey was to obtain a position and estimated visual magnitude for every star down to 10.0 magnitude inclusive, but the faint limit is confirmed from comparisons with other catalogs to be somewhat below 10.
The BD and CD data were presented as catalogs and also as atlases where the positions of all stars were plotted as star maps. The BD and CD are available in machine readable form from http://xml.gsfc.nasa.gov/archive/catalogs/1/1122/index.html
Begun in the early 1900s, the intent of the HD catalog was to provide spectral classifications of all stars down to the faintest possible magnitude limits of the object-prism plates available at the time. This goal was achieved with complete coverage down to about magnitude m(pg)=9 in the original catalog published by Cannon and Pickering (1918-1924). The catalog was subsequently extended to fainter stars in selected areas of the sky. These extensions were published by Cannon in 1936, and by Cannon and Mayall in 1949. The prefix "HDE" is sometimes applied to stars from the extension catalogs.
A nice description of this catalog is available at the Sommers-Bausch Observatory web site http://lyra.colorado.edu/sbo/sboinfo/readingroom/hd.html
The HD catalog was funded from the estate of Dr. Henry Draper, an amateur pioneer in astronomical photography (see his biography at http://www.ras.ucalgary.ca/~gibson/draper/ )
The original National Geographic Palomar Sky Survey was completed in 1954 using the 48-inch Schmidt telescope at Mount Palomar. The telescope exposed 14-inch square photographic plates, each encompassing roughly 6x6 degrees of the sky. The survey was originally intended to cover the entire sky from +90 degrees declination down to -24 degrees (plate centers) in 879 regions, using both red and blue sensitive emulsions, and including stars to magnitude +22. Ultimately the survey was extended to plate centers at -30 degrees (both red and blue), an additional 57 regions. Finally, the Whiteoak Southern Extension was added in 1962 (red plates only), with another 100 plates which extended the set down to a declination of -42 degrees plate center. The UF collection of the Palomar Sky Survey includes 14" x 17" negative prints of all 1,972 exposures, plus the 1981 Transparency Overlay Maps generated by Dixon et. al. of the Ohio State University Radio Observatory.
See http://www.astro.caltech.edu/~wws/poss2.html for details about the southern extension and a northern repeat of the POSS called POSS II.
Today, all of these sky images are available online in digital format from
the DigitizedSky Survey (DSS) site at
http://archive.stsci.edu/cgi-bin/dss_form
This GCVS edition contains data for 28484 individual variable objects discovered and named as variable stars by 1982 and located mainly in the Milky Way galaxy. Portions are available in machine readable form from http://xml.gsfc.nasa.gov/archive/catalogs/2/2214A/index.html
This is the 5th edition of a series of lists intended to help observers pick binary stars of interest. The editors were Wood, Oliver, Florkowski., and Koch. It is available in machine readable form from http://xml.gsfc.nasa.gov/archive/catalogs/6/6044/
A few copies are still available from John Oliver at UF.
The Eighth Catalogue of the Orbital Elements of Spectroscopic Binary Systems is a resource available on the internet in HTML format, created by Alan H. Batten, J. Murray Fletcher, & D. G. MacCarthy from the Dominion Astrophysical Observatory, Victoria, British Columbia, Canada. It is designed for astrospectroscopists interested in observing the spectra of spectroscopic binary stars (SBs). This catalog is available on line at http://ad.usno.navy.mil/wds/dsl/SB8/sb8.html
This is the primary, all around, web accessed astronomical data center.The main CDS web site is at http://cdsweb.u-strasbg.fr/CDS.html
The SIMBAD astronomical database provides basic data, cross-identifications and bibliography for astronomical objects outside the solar system. SIMBAD can be queried by object name, coordinates, other criteria (filters), and lists of objects.
VizieR provides access to the most complete library of published astronomical catalogues and data tables available on line, organized in a self-documented database. Query tools allow the user to select relevant data tables and to extract and format records matching given criteria.
Aladin is an interactive software sky atlas allowing the user to visualize
digitized images of any part of the sky, to superimpose entries from astronomical
catalogs or personal user data files, and to interactively access related data
and information from the SIMBAD, NED, VizieR, or other archives for all known
objects in the field.
Aladin is particularly useful for multi-spectral cross-identifications of astronomical
sources, observation preparation and quality control of new data sets (by comparison
with standard catalogues covering the same region of sky).
The poles of the Earth describe a circle on the celestial sphere 47° in diameter every 26,000 years. Since the Right Ascension and Declination coordinate system is tied to the location of the Celestial Equator and its poles, the coordinates of star are changing continuously. Because the Earth's mass is not spherically sysmetrical (i.e. the Earth bulges at the equator) the gravitational attraction of the Sun and the Moon (and to a much lesser degree, the planets) causes the Earth's axis to precess slowly like a top. The result is that the Vernal Equinox moves to the west at a rate of about 50 arcseconds per year (for a full revolution in about 26,000 years). The result is that though the "true" sidereal rotation of the Earth takes 86164.100 seconds, the rotation relative to the equinox (and hence relative to 0 hours RA) takes 86164.092 seconds.
http://www-istp.gsfc.nasa.gov/stargaze/Sprecess.htm
http://www.crystalinks.com/precession.html
A tool to precess coordinates http://fuse.pha.jhu.edu/cgi-bin/precess_tool
This page was last edited September 18, 2003 1:34 PM