Web Interface GuideThis document describes the use of each of the fields on the SkyView Web forms. When using SkyView you should be able to click on the field label to go directly to the relevant portion of the document. Only the Coordinates/target field and the survey are mandatory. All others are optional.
This interface is a Web portal to SkyView-in-a-Jar, a Java implementation of the SkyView geometry engine. The fields on the web form correspond to settings used there. Detailed information on these parameters, parameter values, and algorithms is given in the User's Guide. The relevant setting is indicated here.
Also included in this document is some information about the results page generated from the Query Form
Overall Organization of the Query Form
SkyView now uses a single query form for all requests. When the form first appears many options are hidden. You can reveal options by clicking on the
arrow
links in the page. The will turn into
and a set of options will be displayed.
You can click on to hide the options,
but any changes you have made will be saved.
Submit and Reset
Submit
- Pressing this button submits the request to be processed by SkyView. You can also submit requests by entering a carriage-return in any text input field.
- Pressing this button restores all fields to default values, clears survey selections and in general returns the form to the state which it had when the you first entered it.
Results Window
- When "Display results in new window" is checked, results will be shown in a window with the target name of "newwin" rather than the current window. I.e., only one new window will be opened regardless of the number of requests you make.
Required Parameters
- SkyView-in-a-Jar setting: Position
- This field is used to determine the center of the field to be retrieved. If you specify coordinates these are used as the center. When equatorial coordinates are being used the RA may be specified as either hh mm ss or ddd.fff, i.e., in hours or in decimal degrees. The coordinate fields may need to be separated by a comma or sign of the declination
- Usually if any letter is used in this field the field is assumed to be an object name and is sent to the SIMBAD or NED name resolver to be converted to coordinates.
- Examples:
6 45 10.76 -16 41 57.82 6 45 10.76, -16 41 57.82 101.2948411 -16.6993947 101.2948411, -16.6993947 sirius - This field is used to determine the center of the field to be retrieved. If you specify coordinates these are used as the center. When equatorial coordinates are being used the RA may be specified as either hh mm ss or ddd.fff, i.e., in hours or in decimal degrees. The coordinate fields may need to be separated by a comma or sign of the declination
- SkyView-in-a-Jar setting: Survey
- These selection boxes allows you to select data from one or more surveys. You can select multiple surveys either by dragging the mouse down the box with the button pressed, or pressing the control-key simultaneously with the mouse button when adding new selections (note: some browsers behave differently with mulitple selects). The surveys are described in detail in the Survey Document.
- The surveys are divided according to wavelength regime and any number of surveys in any number of the different regimes may be selected. Note that when you click on a survey in one wavelength regime box you will not de-select any survey that has been selected in another regime. Typically you can use <cntrl>-Click to deselect an entry.
- These selection boxes allows you to select data from one or more surveys. You can select multiple surveys either by dragging the mouse down the box with the button pressed, or pressing the control-key simultaneously with the mouse button when adding new selections (note: some browsers behave differently with mulitple selects). The surveys are described in detail in the Survey Document.
3-D Surveys
Click on the arrow next to "3-D Image Surveys" to show the 3-D surveys options. A 3-D survey has a vector of values for each pixel location, typically giving the intensity as a function of energy at that location. Data may be resampled in both energy and location. The output image may have a single plane -- a simple scalar image -- or have more or fewer planes than the original data. Data is resampled in the third dimension assuming that the intensity is constant throughout a given energy bin. A given output plane is the sum of the values of each input plane weighted according to the fraction of the input plane included in the output.
Offset, bin size and number of bins for 3-D surveys
- SkyView-in-a-Jar setting: Ebins
- The offset gives the 0-based offset of the start of the first bin the user wishes. The bin size gives the number of input bins to be placed in each ouput bin. The number of bins gives the number of output bins to be generated for a 3-D survey. E.g., if the survey has 10 input bins (e.g., EGRET), and the user wishes to compress all of this data into 3 output energy bins, the numbers could be 0,3.33333,3. The 10 input bins will be sampled into three output bins. If we just wanted to compress by a factor of two and drop the first and last bins, then 1,2,4 would be appropriate.
Fields in Commonly Used Parameters
Click on the Arrow next to "Commonly Used Parameters" to see these fields. All of these parameters are optional.Coordinates
- SkyView-in-a-Jar setting: Coordinates
- Click on this field to choose among common equatorial, galactic and ecliptic coordinates, or enter a special coordinate in the entry box if you want a less commonly used system. See the user's guide for details on the supported coordinate systems and their names.
- SkyView-in-a-Jar setting: Projection
- Click on this field to choose among the map projections:
Gnomonic (Tan) -- good for small regions. Rectangular (Car) -- simplest projection. Aitoff (Ait) -- Hammer-Aitoff, equal area projection good for all sky maps. Orthographic (Sin) -- Projection often used in interferometry. Zenith Equal Area (Zea) -- equal area, azimuthal projection. COBE Spherical Cube (Csc) -- Used in COBE data. - Click on this field to choose among the map projections:
- SkyView-in-a-Jar setting: Pixels
- You may select the pixel dimensions of the image to be produced. A scalar value or a pair of values separated by comma may be given. If the value is a scalar the number of width and height (in pixels) of the image will be the same. By default a 300x300 image is produced. Note that pixels need not be square.
- SkyView-in-a-Jar setting: Size
- This field sets the size of the image in degrees. A single value or a pair of values separated by comma may be given. If a single value is given the angular size will be the same in both width and height.
- Note that the default size for an image is the number of pixels times the intrinsic pixel size of an image.
- Previous versions of SkyView did not support non-square pixels so that only a scalar value of size was supported and this always referred to the width or height of the image, whichever was larger in pixels. Now if when a scalar value is supplied, the number assumption is that the angular dimension is the same in both height and width, and if the number of pixels are not the same in the two directions, the pixels will not be square.
- This field sets the size of the image in degrees. A single value or a pair of values separated by comma may be given. If a single value is given the angular size will be the same in both width and height.
Image pixel format
Other Optional Parameters
These options are a little less frequently used. Clock on the
arrow next to "Other Optional Parameters" to reveal them.
Brightness scaling
- SkyView-in-a-Jar setting: Scaling
- This field selects the transformation between pixel intensity and intensity on the displayed image. The default logarithmic scaling generally works well over the entire image. Linear scaling tends to enhance bright features. Sqrt scaling is intermediate between the first two and is close to the response of the eye. Histogram equalization scaling can sometime show subtle features in the data.
- SkyView-in-a-Jar setting: Sampler
- Once SkyView has retrieved the data requested, it needs to be resampled so that it can be displayed. SkyView offers several ways to do this. The default , is the nearest neighbor approach, but linear interpolation, a flux conserving, exact-area, clipping resampling, and higher order Lanczos and Spline resamplers are availabe.
- SkyView-in-a-Jar setting: Rotation
- This gives the rotation of the image in the projection plane.
- SkyView-in-a-Jar setting: Resolver
- The name resolver box allows you to choose a name resolver to use when looking up a name entered in the coordinate value box (as opposed to a numeric coordinate value). The default choice (as also used in the basic form) is to call the SIMBAD name resolver first and then the NED name resolver if the SIMBAD search fails.
- SkyView-in-a-Jar setting: Deedger
- When multiple input images with different backgrounds are resampled the edges between the images may be apparent because of the background shift. This field allows the user to attempt to minimize these edges by applying a de-edging algorithm. The user can elect to choose the default given for that survey, to turn de-edging off, or to use the default de-edging algorithm.
- SkyView-in-a-Jar settings: Smooth
- You can choose to do a boxcar smoothing of the image prior to the image display. The size of the boxcar in pixels should be entered here. The boxcar need not be square so a pair of values separated by commas may be given. If the value is less than or equal to one then no smoothing is done. Since boxcar smoothing works only with odd values, an entered even number will have a one added to it.
- SkyView-in-a-Jar setting: LUT
- Choose from the color table selections to display the data in false color.
- You may invert the color table by checking the "Use inverse" box.
- Choose from the color table selections to display the data in false color.
Optional Overlays
These options let you draw information on top of the images. Click on the arrow next to "Optional Overlays" to reveal them.Plot Color
- SkyView-in-a-Jar setting: PlotColor
- The color of the plot overlays can be changed by entering the name of a color in this field.
Overlays only
RGB overlays
- SkyView-in-a-Jar settings: RGB, RGBSmooth
- You can generate true color images by selecting an image for each of the primary colors. The image is displayed as a JPEG.
- A square box-car smoothing can be applied to each image before combining the three colors. The smoothing should be given as a trio of values, for the R, G and B planes of the image respectively.
- You can generate true color images by selecting an image for each of the primary colors. The image is displayed as a JPEG.
- SkyView-in-a-Jar settings: Catalog, CatalogIDs, CatalogFilter, CatalogRadius
- The catalog overlays box allows you to ask that the positions of catalog objects be marked on the image. A listing of all objects found with their position will be generated. Multiple catalogs may You can select HEASARC catalogs from the table provided, or select Vizier catalogs using the input field. Any Cone Search URL may also be entered there.
- The 'Display ID Strings' checkbox controls whether the IDs of the returned catalog elements will be shown.
- Catalog entries can be filtered using a 'Catalog filter'. E.g., if the table has a 'vmag' field, then vmag<10 will select out the brightest objects.
- A catalog radius field may be used to select objects only in some region interior to the image boundaries.
- The catalog overlays box allows you to ask that the positions of catalog objects be marked on the image. A listing of all objects found with their position will be generated. Multiple catalogs may You can select HEASARC catalogs from the table provided, or select Vizier catalogs using the input field. Any Cone Search URL may also be entered there.
- SkyView-in-a-Jar setting: Contour,ContourSmooth
- You can choose to display the contours of an image over using this option. More than one image can be contoured, but the contours of different images are not distinguished and the scaling options if specified apply to all.
- The spacing of the contours is controlled by the 'Contour Scaling' options, and you can also set the minimum and maximum contour levels as well as the number of levels.
- The image can be smoothed by a boxcar smoother before being the contours are drawn.
- You can choose to display the contours of an image over using this option. More than one image can be contoured, but the contours of different images are not distinguished and the scaling options if specified apply to all.
SkyView Query Form Results Page
This page displays images generated from the SkyView Query Form.
The criteria used to generate each image is listed along with some information
about the survey. More survey information can be found by following the More Information link. Options to download the image and FITS files are presented.
SkyView Image Gallery
If an image size is below a certain pixel
size limit the user will see the Add to Gallery button. If clicked
the original image (previous to applying the zoom feature) will be added to
the pool of images that are displayed on the SkyView Image Gallery.
The images will also be randomly selected to appear on the main SkyView page . Images will stay on the system until a directory size limit is reached at which time they will be deleted. Older files will be deleted first.
SkyView Home | Help | Survey Information | Non-Astronomers Interface | Query Form
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.
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