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More advanced ways to access the Elodie archive

The user interface of the Elodie archive has been designed to be used either from a web browser or by a program. This latter feature, a fundamental principle of the Virtual Observatory, allows web-based services to transparently access the archive.

Accessing the catalogue of observations

The request returns an HTML page with all spectra of VEGA available in the archive. As the HTML format may not be convenient to use in a text editor or in a program, you can modify the request by asking for ASCII format:

Although this plain-text format is the only machine-oriented format now available for the catalogue, we may provide a tab-separated format (tsv) or VO_table format in the future.

To download the content of an URL on a user's computer, it is very natural to use a browser, such as Mozilla, Netscape or even Internet Explorer, but this is not the only solution. In practice, a browser is only one of the clients that may be used to access the Web. Other common clients are the so-called "crawlers" which can recursively download files from the web. A common one is wget, present on most recent Linux distributions (but several alternatives exist). In the following we will give examples with wget.

From a shell window, you can download the list of observations of Vega (see above) as:

wget "" -O vega.txt

Accessing CCF results directly (NEW)

Complete CCF results for a given star can be obtained by entering a command with parameters in your browser. For example the command below will list in HTML format all the CCF results for HD190007 contained in the cross-correlation internal table (identified by n=501) :

By replacing a=htab by a=t you obtain a simple ASCII table with columns separated by tab marks. In order to limit the number of metadata appearing in the table you can also type :,datenuit,imanum,exptim,masque,vfit,sigfit,ampfit

To submit a query concerning a specific group of stars, for example all stars in the Gliese catalog, or all Henry Draper stars with names beginning with HD190, use the parameter o=GJ% or o=hd190% :,datenuit,imanum,exptim,masque,vfit,sigfit,ampfit,datenuit,imanum,exptim,masque,vfit,sigfit,ampfit

Please note that some ELODIE identifiers (objname) are still incorrect. We correct these as they appear.

Downloading FITS files directly

Suppose you are interested in all the spectra of Vega and want to download the FITS files to your disk. You can naturally go to the web interface with your favorite browser and download each spectrum one by one. But you can also issue the commands from the shell. For example:

wget "" -O 19960502_0041.fits

In the URL above you recognize the unique identifier of a file in the archive. You may construct similar URLs for any file in the archive. If you are a familiar with a text editor (such as emacs, pico or nedit) and with Unix shell commands, you can readily write a procedure to download all the files you desire.

So, now you know how to easily download archive spectra in the s2d format. But you may wish instead the more easy-to-use reconnected, resampled spectra, or continuum normalized spectra. This is easy to do: just add the pipeline command to the URL. For example to get the resampled spectrum use:

wget "" -O 19960502_0041.fits

The pipeline command is the value of the z= parameter in the URL. You may analyze how the pipeline works by watching the customize menu, and then produce your own pipeline command. You can also read the documentation.

Useful shell scripts

Two scripts are available to handle ELODIE data (require bash shell):

  • Script to retrieve a list of observations for a list of stars from the ELODIE archive (
  • Script to retrieve a list of spectra for a list of observations from the ELODIE archive (

Accessing FITS files directly from astronomical packages

We have seen that the archive can be accessed with wget and we said that other clients may be used. Actually many astronomical packages can directly read a FITS file over the Internet by giving an address http://... or ftp://... in place of the name of the file in the local file system.

For example, by using the Pleinpot package, you may copy a remote file to a local disk file by typing:

copy "[]" 19960502_0041.fits

or plot a spectrum by typing:

hisvis "[]" @5

Upcoming feature: how to retrieve spectra with specific characteristics

Dernière mise à jour : 29 Mar 2014