Frequently Asked Questions
What is SkyView?
SkyView is a "virtual" observatory dynamically generating images
of the sky in different wavelength regimes from a static image database.
SkyView is intended as a quick look facility to see the heavens.
What do you mean by "virtual" observatory/telescope?
SkyView is not a real telescope but a large database of
astronomical image surveys that simulate the images taken by
telescopes or satellites.
What do I need to use SkyView?
Any modern Web browser should do fine.
How does SkyView work?
The core of SkyView is a geometry engine which enables it
to transform data from existing surveys into the image you have
requested. The step by step workings are shown in the
SkyView Works help page.
Can I freely reprint images obtained in SkyView?
Yes, with limited exceptions (most notably the Digitized Sky Survey).
Copyright information for a given survey is included in the text
beneath a returned image.
How can I acknowledge SkyView in my publications?
We do not require mention of SkyView in any publication using
SkyView generated images. If you wish to acknowledge
SkyView (and we would be pleased if you
did) please use the following statement:
"We acknowledge the use of NASA's SkyView facility
(http://skyview.gsfc.nasa.gov) located at NASA Goddard
Space Flight Center."
- Note, SkyView is intended to be italicized in any usage.
How do I reference SkyView?
Please use the following reference:
McGlynn, T., Scollick, K., White, N., SkyView:
The Multi-Wavelength Sky on the Internet, McLean, B.J.
et al., New Horizons from Multi-Wavelength
Sky Surveys, Kluwer Academic Publishers, 1996,
IAU Symposium No. 179, p465.
Why isn't the survey I want included in SkyView?
SkyView comprises only of image surveys in the public domain or
are used by permission of the author. We are always looking for new
surveys. If you feel we should include something, please let us know
where we can find it.
Can I download the SkyView code?
- Yes. The internal SkyView code is freely available in the SkyView-in-a-Jar download.
You can also download batch scripts to access our on-line services from the command line. See the
SkyView clients page for more information.
How do I find out information regarding the surveys in
The Surveys document contains an
overview regarding the surveys included in SkyView. Each section
provides references to more detailed descriptions in the scientific
literature and/or documents on the web.
How do I use SkyView?
At its simplest, enter a coordinate value and select one or more surveys
and click "Submit" (these are called the required parameters). In addition,
there are optional parameters that allow to have creating control over
the geometry and display of the image.
For an explanation of the different options check the
Web Interface Guide.
How do I enter coordinates?
The coordinate position can be entered either as a name (recognized by
either the SIMBAD or NED name resolvers) or in longitude, latitude (or
R.A. , DEC in case of equatorial coordinates). When entering coordinates
with longitude and latitude, separate the two values with a comma or start
the latitude value with either a +/-.
For examples, please check the SkyView
Web Interface Guide
What are the selection boxes underneath the surveys selection?
The optional parameters allows you to change to default geometry and display
of the returned image. Also, there is an overlay section
to add catalogs, contours, and produce three color images. For more detail
please refer to the SkyView
Web Interface Guide.
How do I change the color table?
The color table can be changed by selecting a color table in the Other Options section on the Query Form.
How do I get just a catalog overlay (without an image)?
You can get just a catalog overlay by selecting one or more catalogs (but
no more than ten) in the Overlays section of the Query Form and setting
up the geometry just as you would for an
image survey (i.e. you need to enter coordinates or a name in the
coordinate value box). The biggest exception is that the Image size
must be set to a numerical value (default has no meaning in this case).
The important step is to check the Plot Overlays Only (no image) box
in the Overlays Preferences area.
Submitting your request will return an image page with the catalog
What is the X-windows interface?
The X-Windows interface has been replaced with the web and Java
Why are images returned as JPG and FITS files?
The image is in JPG format for display purposes only. To obtain the
raw data of the displayed image for use in further
processing at your site, we provide a link to the FITS file. Note, overlays
(catalog, contour, grid, etc.) will not appear on the
What is FITS?
- The Flexible Image Transport System (FITS) is an image format devised by
astronomers to store images and catalog information. A FITS file contains
a text header describing the image, and a byte array containing the image
data. A FITS can also contain tables (quite useful for catalogs). For a
more complete treatment of FITS please refer to
How do I get a FITS reader?
freely available for UNIX, Windows, and Macintosh from NRAO.
How do I compare a SkyView image with data I have?
To align an image you have with SkyView, you need to know the
geometry of your data. From that, you can set up the optional
parameters such that
the return image with overlay exactly onto your image.
What are the units of the data returned?
The units for a given survey is included in the information provided in
the Surveys document. When an image
page has returned, click on the "More info" link to view this
Does SkyView adjust the pixel values for the pixel size?
Most SkyView surveys have intensive units, i.e.,
the value for a pixel is independent of the size of the pixel. A few
surveys have extensive units where the pixel value should be scaled
according to the size of the units. This correction is not currently
What is the precision of the data returned?
The positional accuracy of objects in an image are within the
of the survey which can vary wildly from survey to survey. The spatial
resolution for a survey is available in the
document or by clicking the "More info" link on the image
Where is the image?
The returned image page is designed to appear in a new web browser
window. If you don't see the image page after a request is finished,
check to make sure that the window is not being hidden by other
windows. Even if SkyView failed for some reason, a blank page
How come nothing returned?
Normally, if an error occurs, the image page returns detailing with the
nature of the error. If the page returns blank, a serious error
has occurred, and we request that you send us an e-mail so we can
fix this as quickly as possible.
Why can't I find a planet, comet, sun, moon, etc.?
In general, objects that are not of fixed position in the sky (i.e.
just about everything in the Solar system) are not viewable
in SkyView. The image database is static in that the images were
taken at a fixed point in the past.
How do I find the star I bought?
Buying a star has entertainment value but these "bought" stars hold no
official standing in the astronomical community (star names are
maintained by the International Astronomical Union). Usually, you are
given the coordinates as well as the name of the star. By entering
the coordinates, you can find "your" star, but you will be unable to
enter just the name in the coordinate field box. More information can
be found at the IAU site.
Why does it take so long to get an image?
A lot depends on the size of the request (relative to the survey scale)
and network traffic. The default settings typically an image in
10 to 30 seconds (in good conditions). Adding other options
can delay the request. Note that at peak times during the day
five or more requests may be being processed simultaneously. We have
recently (May 2007) upgraded the processors used within SkyView .
Requests time out in a generous amount of time so that very large
requests may not return. There are restrictions on the size of the
image that can be requested from the higher resolution surveys which
put some limits on the length of a request. A common problem causing
requests to time out, is to ask for a catalog overlay of a very large
region from a very large catalog (especially the Guide Star Catalog).
The Java interface is roughly 400kb in size (it must all download before
the interface pops up). The retrieved images are based off of the FITS
files created for the request and are roughly 350kb in size. We
no longer support this interface but we continue to make it available.
Whom do I contact when I have a problem or question?
Send questions and comments to
How do I become an astronaut/get a job with NASA?
For potential astronauts please refer to
For job opportunities please refer to
Why couldn't I connect to SkyView?
Occasionally, our network server will go down or not take network
traffic (usually due to maintenance). These down times are normally
scheduled for the weekend, and we give advance warning as best we can.
Network traffic can be a fickle thing. If you have trouble connecting,
please send us e-mail, and we'll check to see if the problem is on
Where can I get a picture of the major things in the sky tonight?
- Check our Astronomy Links
page for links to sites that provide star charts.
Direct all questions regarding SkyView to our Feedback Page
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/
Astrophysics Science Division.
We gratefully acknowledge the support of NASA and contributors
of SkyView surveys.