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General Questions

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General 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 How 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 SkyView?

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.

Using SkyView

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 SkyView 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 overlay positions.

What is the X-windows interface?

The X-Windows interface has been replaced with the web and Java interfaces.

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 FITS image.

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 our FITS site

How do I get a FITS reader?

A host of FITS readers are described at this

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 page directly.

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 applied.

What is the precision of the data returned?

The positional accuracy of objects in an image are within the spatial resolution of the survey which can vary wildly from survey to survey. The spatial resolution for a survey is available in the Surveys document or by clicking the "More info" link on the image page.

Problems

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 should return.

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?

See our blog entry on this topic.

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 get an image in just a few seconds for most surveys. 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).

Note that in some cases, SkyView must first download source data from another remote site (e.g., WISE, SDSS, UKIDSS, ...). We can't start resampling the data until we've gotten the original information. We cache images retrieved from remote surveys, so as time goes by access to these becomes faster.

Whom do I contact when I have a problem or question?

Send questions and comments to
       Skyview Feedback 
       

Miscellaneous

How do I become an astronaut/get a job with NASA?

For potential astronauts please refer to
http://liftoff.msfc.nasa.gov/academy/astronauts/wannabe.html

       
For job opportunities please refer to
http://www.nasa.gov/about/career/index.html
       

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 our end.

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.


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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/ 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

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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