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Running SkyView on Your Machine

In addition to running SkyView on the Web, you can run SkyView in applications and scripts on your local machine. SkyView supports two different approaches for this.

Since the SkyView web server is itself running the same software packaged in the SkyView-in-a-Jar you can use the User's Guide to get a detailed understanding of all of the arguments that are available for either approach. On this page we briefly describe how URLs are parsed into settings that are passed into the Web server's SkyView-in-a-Jar and then review some of the most commonly used settings.

When SkyView-in-a-Jar is run from the command line, settings may be given in input files or on the command line using keyword=value strings. When we access SkyView over the Web, settings are extracted simply by taking the CGI keyword=value parameters and making them the settings for the run. The user is free to specify any settings with the exception of the the location of the output files (Output) and caches (Cache). Some settings do not make much sense in the Web environment but typically they are ignored if they cannot be used.

Download and Documentation page:

SkyView web server scripts
Another easy way to build and retrieve SkyView URLs is using the skvbatch and webquery Perl scripts we provide (skvbatch calls webquery). These are old and very simple Perl scripts and may not work behind firewalls. To address this problem we have recently created the Perl script that uses wget, a more robust retrieval package that runs on most UNIX-like operating systems as well as Microsoft Windows. wget is included with most systems. To download wget or get more information visit the GNU website.


It is also possible to build the URL explicitly and using wget or curl may be your easiest option, or feel free to modify our scripts to your requirements.

Note: The AF_INET and SOCK_STREAM values in webquery (lines 62 and 63) are operating system dependent. Please check your socket.h file (usually located in /usr/sys/include/sys or something similar) for the proper values and update webquery accordingly. You may also need to change the first lines of the scripts to point to your local version of perl.

To use these just enter something like the following examples (syntax is the same for skvbatch and skvbatch_wget):
     skvbatch file=FILE [key=Value key=Value etc.]


    Example 1
         skvbatch file=example1.fits position='+12 34, -10 23'  \
                  Survey='Digitized Sky Survey'

    Example 2
         skvbatch file=example2.fits Position=hd184927 \
              Survey='Digitized Sky Survey' LUT=Fire \

    Example 3
         skvbatch file=example3.fits Position='+12 34, -10 28'  \
		  Catalog='SAO STAR CATALOG' Size=5 Pixels=500

    Example 4
    Perl script to do multiple queries
        $i = 0;
        @array = ("'3c273'","'0 41, +41 5'","'crab nebula'",
                  "'14 21 23.2, -12 24.3'");
        foreach (@array) {
           system("skvbatch Position=$_ Survey='Digitized Sky Survey' 
		Catalog='HST guide stars (1.1)' Return=gif Grid 
		Pixels=400,200 file=$filename");
    Example 5
    Perl script to retrieve a RGB image
    Retrieving an RGB images with a skvbatch script is slightly more involved. 
    The skvbatch script was designed with the idea of the user retrieving a 
    single output file.  In a typical SkyView request there are two images 
    produced: the FITS file and the quicklook image.  The user gets to pick 
    the image they want by specifying the return format.  However with RGB 
    requests there are four images produced and three of them are in the same 
    format.  We currently do not provide a way of parametrizing the request 
    to get the specific file the user wanted.  However we do provide a way 
    to get back the stem that SkyView is using in generating all of the 
    files. The "return=filename" parameter setting can be used. This returns 
    just a single string which you can use to build the full URLs pointing 
    to any of the files generated in the RGB image construction.  If, for 
    example, skvbatch returns a value XXX then the four files are:

   With this stem you can easily retrieve the JPEG image directly.  Here  
   is a little C shell script that you can use to get RGB JPEGs.

	set name=`skvbatch survey=dss,dss2b,dss2r rgb=t position=3c273 return=filename`
        wget${name}_rgb.jpg -O rgb.jpg


The file argument is case sensitive since it is handled locally by the Perl scripts. The keywords sent to SkyView are not case sensitive, nor are most (but not all) values.

Once executed, a FITS file is returned into the file specified on the command line (or to standard output if no file is given).

Quotes are only necessary for values that contain blank spaces.

URL examples

Fits data and images can also be accessed via a URL. The parameters below can also be used to customize your URL request. As an example, the following link would return a 300x300 (default size) Digitized Sky Survey FITS file centered at RA 14.5, Dec 36.5:,36.5&Return=FITS

The following returns an GIF image with a grid and catalog overlay:

Commonly Used Parameters

We briefly review a few of the most commonly used settings, but the User's guide describes nearly 100 different settings. Note that the keywords used here differ from earlier versions of the Batch interface. Those earlier keywords are also supported. Section 2.4 on Batch Compatibility mode in the User's Guide discusses the support of the earlier style of keywords.
    Position=name/value         - Coordinate position or name 
    Survey=survey[,survey,...]  - Survey[s] to generate images from
    Coordinates=value           - Coordinate system (e.g., J2000, B1950, Galactic, ICRS)
    Projection=proj             - Map projection (Tan, Sin, Car, Ait, Zea, Csc)
    Scaling=scl                 - Brightness scaling (Log, Linear, Sqrt, HistEq) 
    Size=size[,size]            - The size[s] of the image in degrees.  If only
                                  one value is given the image is square.
    Pixels=n[,m]                - The number of pixels in the image.  If only one
                                  value is given the height and width are the same.
    Catalog=catalogs[,catalog]  - The name of the catalog[s] to be queried.  Each name
                                  can be a HEASARC short name, a  Vizier catalog name,
				  or a VO Cone Search base URL.
    Smooth=value[,value]        - dimension[s] of smoothing box.
    Sampler=samp                - Sampling to use (NN, Lin, Clip, Lanczos, Spline)
    Resolver=res                - Resolver to translate names to coordinates 
                                  (SIMBAD-NED, NED-SIMBAD, NED, SIMBAD)
    Grid=[Coords]               - Overlay a grid on the image [in a given coordinate system]
    LUT=name                    - Use the given lookup table to translate brightness to color.
                                - Overlay contours from the given survey using
				  the given scaling (Linear, Log, Sqrt).  The
				  user can optionally specify the range and number
				  of contours.
    RGB                         - If this is specified three values are
                                  expected in the survey field and these
				  will be used to generate a three-color
				  image as Red/Green/Blue.

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SkyView has been developed with generous support from the NASA AISR and ADP programs (P.I. Thomas A. McGlynn) under the auspices of the High Energy Astrophysics Science Archive Research Center (HEASARC) at the NASA/ GSFC Astrophysics Science Division.

We gratefully acknowledge the support of NASA and contributors of SkyView surveys.

A service of the Astrophysics Science Division at NASA/ GSFC
and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory (SAO)

HEASARC Director: Dr. Alan P. Smale
HEASARC Associate Director: Dr. Roger Brissenden
Responsible NASA Official: Phil Newman
Web Curator: Laura McDonald

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