Alasdair Allan

NAME

Astro::DSS - An Object Orientated interface to the Digital Sky Survey

SYNOPSIS

  $dss = new Astro::DSS( RA        => $ra,
                         Dec       => $dec,
                         Target    => $object_name,
                         Equinox   => $equinox,
                         Xsize     => $x_arcmin,
                         Ysize     => $y_arcmin,
                         Survey    => $dss_survey,
                         Format => $type );

  my $file_name = $dss->querydb();

DESCRIPTION

Stores information about an prospective DSS query and allows the query to be made, returning a filename pointing to the file returned.

The object will by default pick up the proxy information from the HTTP_PROXY and NO_PROXY environment variables, see the LWP::UserAgent documentation for details.

It will save returned files into the ESTAR_DATA directory or to TMP if the ESTAR_DATA environment variable is not defined.

REVISION

$Id: DSS.pm,v 1.7 2003/02/21 18:52:15 aa Exp $

METHODS

Constructor

new

Create a new instance from a hash of options

  $dss = new Astro::DSS( RA        => $ra,
                         Dec       => $dec,
                         Target    => $object_name,
                         Equinox   => $equinox,
                         Xsize     => $x_arcmin,
                         Ysize     => $y_arcmin,
                         Survey    => $dss_survey,
                         Format    => $image_type );

returns a reference to an DSS query object.

Accessor Methods

querydb

Returns a filename of the image returned from a DSS query.

   $filename = $dss->querydb();
proxy

Return (or set) the current proxy for the ADS request.

   $query->proxy( 'http://wwwcache.ex.ac.uk:8080/' );
   $proxy_url = $query->proxy();
timeout

Return (or set) the current timeout in seconds for the DSS request.

   $dss->timeout( 30 );
   $proxy_timeout = $dss->timeout();
url

Return (or set) the current base URL for the DSS query.

   $url = $dss->url();
   $query->url( "archive.eso.org" );

if not defined the default URL is archive.eso.org

agent

Returns the user agent tag sent by the module to the ADS server.

   $agent_tag = $dss->agent();
RA

Return (or set) the current target R.A. defined for the DSS query

   $ra = $dss->ra();
   $dss->ra( $ra );

where $ra should be a string of the form "HH MM SS.SS", e.g. 21 42 42.66

Dec

Return (or set) the current target Declination defined for the DSS query

   $dec = $dss->dec();
   $dss->dec( $dec );

where $dec should be a string of the form "+-HH MM SS.SS", e.g. +43 35 09.5 or -40 25 67.89

Equinox

The equinox for the R.A. and Dec co-ordinates

   $equinox = $dss->equinox();
   $dss->equinox( "2000" );

defaults to 2000.

Target

Instead of querying DSS by R.A. and Dec., you may also query it by object name. Return (or set) the current target object defined for the DSS query, will query SIMBAD for object name resolution.

   $ident = $dss->target();
   $dss->target( "HT Cas" );

using an object name will override the current R.A. and Dec settings for the Query object (if currently set) and the next querydb() method call will query DSS using this identifier rather than any currently set co-ordinates.

Xsize

The x extent of the DSS image to be retrieved in arcmin.

   $xsize = $dss->xsize();
   $dss->xsize( 20 );

Image sizes for FITS, gzipped FITS and GIF are 260kB, 110kB and 70 kB respectively for a field of 10*10 arc minutes. There's a limit of around 4 MB for the largest image to be delivered. Images from the DSS2 are bigger, because the pixel size is smaller.

Ysize

The y extent of the DSS image to be retrieved in arcmin.

   $xsize = $dss->ysize();
   $dss->ysize( 20 );

Image sizes for FITS, gzipped FITS and GIF are 260kB, 110kB and 70 kB respectively for a field of 10*10 arc minutes. There's a limit of around 4 MB for the largest image to be delivered. Images from the DSS2 are bigger, because the pixel size is smaller.

Survey

The survey to return

   $survey = $dss->survey();
   $dss->survey( "DSS1" );

valid choices are DSS1, DSS2-red, DSS2-blue, DSS2-infrared. The entire DSS1 data is stored on magnetic disks at the ESO-ECF Archive. DSS2 is stored on DVD-ROM in a juke box. Retrieval time takes about less than 5 seconds for a DSS1 field and less than 20 seconds for a random DSS2 field in the juke box.

The DSS1 survey is 100% complete, while the DSS2-red now covers 98% of the sky; DSS2-blue 45% of the sky and DSS2-infrared 27% of the sky.

Format

The image format required

   $format = $dss->format();
   $dss->format( "FITS" );

valid format types are FITS and GIF and FITS.gz. The default is to return a GIF Image.

General Methods

configure

Configures the object, takes an options hash as an argument

  $dss->configure( %options );

Does nothing if the array is not supplied.

COPYRIGHT

Copyright (C) 2001 University of Exeter. All Rights Reserved.

This program was written as part of the eSTAR project and is free software; you can redistribute it and/or modify it under the terms of the GNU Public License.

AUTHORS

Alasdair Allan <aa@astro.ex.ac.uk>,