Astronomical Images Over the Web

Many groups are serving and displaying small sections of the sky ("postage stamps"). Current servers and client browsers mostly deal with simple single-wavelength FITS images with World Coordinate System (WCS) sky coordinate to pixel transforms encoded in their headers. See Mark Calabretta and Eric Greisen's paper

Image Servers

Image Browsers

A Test

If you have the line
image/x-fits                   fit     fits    fts     FIT     FITS
in your mime.types file and a browser set up to deal with the image/x-fits mime type by an entry something like this in a mailcap file
image/x-fits;                saoimage -fits %s
you should be able to retrieve and display a FITS image of M51 as shown at the top of this page from http://tdc-www.harvard.edu/postage_stamp/wpix.fits

Mailing List

A mailing list was begun in 1994 as a means for discussing standards and procedures for serving and viewing "postage stamp" images of an arbitrary portion of the sky. Although it has been defunct for several years, the mailing list was intended to include both servers and users of public image databases. Standards for access, such as keywords and coordinate systems, and standards for provided products, such as compression and dealing with image overlaps and gaps were discussed. To avoid unnecessary duplication, work in progress as well as existing products were covered.

Future Goals

Client software is still needed which can be executed from within application programs, in order to compare survey catalogs, overlay information, or facilitate astrometric calibration of optical imagery. A major issue to discuss is the standardization of a compression method (or methods--that is an additional debate). Other tasks include finding ways to deliver multiple simultaneous wavelengths and overlays of catalogued data. It is hoped that any software which is produced be shared with the rest of the community. Incremental goals will be set, so that the large databases can be used as soon as possible.

Last updated 19 November 1997 by Doug Mink dmink@cfa.harvard.edu

Telescope Data Center Center for Astrophysics