SkyView

SkyView is a facility available through the `xray` account which allows access to data from all-sky surveys. By entering the position and size of the region desired and the surveys wanted, the data is extracted, displayed, and formatted in a FITS file.

Over the past decade data from digital all-sky surveys has become increasingly widely distributed, either over the network or through CD-ROM's, but such information has remained hard to use. To look at a piece of the sky with a particular scale, orientation, coordinate system, etc., the user must build or find appropriate conversion routines. SkyView addresses these conversions and immediately provides the image in the desired coordinate system. Users need not worry about the geometry of the observations. They can immediately go on to doing astronomy. This chapter will only introduce SkyView's capabilities. A full description of SkyView is in the "SkyView User's Guide" and "SkyView Design" document, both available by anonymous FTP in the directory /pub/doc on "skview.gsfc.nasa.gov". SkyView also has extensive internal help available.

To start SkyView, type `skyview` at the HEASARC> prompt. This will start the SkyView GUI user interface. Onscreen will appear a single-form interface which will allow you to specify the requested images (and possible catalog or coordinate grid overlays) and output formats (X-display, FITS, and PostScript). Other commands available in the `xray` account will allow you to send any data files you have retrieved back to your home machine (type "help file-transfer" while in the `xray` account for more information).

The current release is essentially a beta test and we hope that users who encounter problems will let us know about them using the addresses below. Note that in the current release you will need to have a X-capable display. To display a typical image takes a minute or so excluding network traffic.

SkyView allows a user to retrieve data from any of the surveys included and to generate an image in:

• equatorial, Galactic, or ecliptic coordinates,
• Gnomonic (tangent), Aitoff, or rectangular projections,
• any equinox,
• any scale, and
• any size.

When survey data is divided into more than a single file SkyView automatically mosaicks the data to create a single image. If the user scale is different from the survey scale, the data is automatically resampled at the user scale. Data can be displayed on an X-terminal and FITS and Postscript files of the output are produced. Files can be retrieved to the user's home institution.

The user can overlay the image with a coordinate grid, positions of SkyView catalog objects, and intensity contours.

SkyView is currently implemented in IDL using IDL widgets. Several standard IDL image display programs are available to manipulate the image, particularly the color table.

The current SkyView holdings include:

• IRAS SuperSkyFlux surveys in four wavebands. 90 arcsecond resolution.

• Preliminary EUVE All-sky surveys in four wavebands. 1 degree resolution.

• HEAO 1 A-2 survey. 1 degree resolution.

• Bonn 21cm survey. 0.5 degree resolution (declination > -17 degrees)

• Catalogs:4c, Uhuru, Bright Star, Bright Nebulae, Dark Nebulae, Dixon, FK5, HII, Markarian, RNGC, Seyfert, UGC

• CGRO EGRET gamma ray survey (30 MeV to 20 GeV) at about 1 degree resolution

• Improved and much higher resolution EUVE data.

• Optical data at 1.7 arcsecond resolution as generated at the ST ScI and distributed by the PASP.

If you have any questions about or problems with SkyView, please contact

        Keith Scollick 301-286-8413 (scollick@skview.gsfc.nasa.gov)

or 

        Tom McGlynn    301-286-7743 (mcglynn@grossc.gsfc.nasa.gov)