Using All-VO AstroScope

As well as using VOExplorer to select VO resources individually and search by position where available using AstroScope you can also use All-VO AstroScope to search all available VO image, catalogue, spectral archives including Vizier Tables around a user defined sky position or object name and radius. You can then easily interact with the returned lists of results, saving those data locally or transfering them into a range of relevant desktop clients (or Applications) to visualise, record and correlate multi archive returns. Note that as of version 1.2.3.1 (May 2009), new capability is provided to search against resource(s) for a list of user supplied positions if desired using a separate Multi Query task available under Actions in VOExplorer.

AstroScope queries Night Time astronomy data resources. If you are interested in solar or STP data then you need to use HelioScope

RA, DEC can be specified in either sexagesimal or degree format, along with a search radius in the same unit.

This page describes usage of All-VO AstroScope. The Reference Help for AstroScope can be found here.

Illustrative Example

Entering the Object or Search Area

In this example, entering the object name "M101" and pressing the binoculars button to the right will resolve the catalogued coordinates for M101 since it is a known Simbad object. The search radius is input as 0.01 degrees.

If you enter a name with more than one entry in SIMBAD, e.g. Virgo, then only one entry will be returned; you are advised to use a precise name or a position (check with [SIMBAD] directly if necessary) unless you intend to search a very large area.

Search the archives

All registered datasets are then queried including Catalogue, Image, Spectral and Timed Data, depending on which you have opted for. For this particular search region, only catalogue, image and spectral records are being searched and are displayed in the default tabular view as shown below. Note that if you enter a large search radius a warning will appear that some resources may not be able to return data for that search. It is normal that there may be many such warnings initially given the thousands of available resources! Where many resources (including all-sky surveys) are being queried in this way the sheer number of returns is likely to overload the visual display, particularly in well observed regions of sky and so the visualisation automatically switches to a tabular view. In fact for an All-VO use of Astroscope this becomes the default. Alternatively, if a positional search is launched on a single or small number of resources pre-selected using VOExplorer, then a radial visualisation will be shown. Hover your mouse on a particular resource returned in order to obtain a tooltip showing a basic description as supplied by the given data centre. The Sloan Digitized Sky Survey (SDSS) image archive is highlighted in the example below, i.e. the search region overlaps with at least one publically available image contained in SDSS DR5:

Click on View to switch between the available visualisation modes (tabular, radial and hyperbolic). The Services Table shown above lists the VO services as they are queried, and the number of records found for the given search in the Results column along with the type of resource in the Capability column. Any access errors encountered, e.g. if a particular service is registered but not currently available, are also indicated in the "Results" column. Of course there is an important distinction between a service showing 0 results and a service being unavailable and returning no results (shown in this column as Error). Click on the "Title" column header to order the list in alphabetical order or type in a keyword in the search box to identify a particular service.

Left click on a particular resource in the table to see further details in the tabs below. Where multiple results are obtained from a given resource, e.g. an image server for a particular mission, further details are provided under the "Results" tab for a selected resource. In this example there are 10 image files available within 0.01 degrees of M101 in the SDSS DR5 image archive. Details for each one are then listed under the Results tab including columns for the filename, image centre position and offset from search position (in degrees) along with the file type. Clicking on the "Offset" column header allows the user to order their results according to the nearest positional matches if desired. Note that in this example as well as 10 SDSS DR5 images there are also 6 entries in the 2XMM X-ray catalogue within this search radius.

Further information about the resource or service is given in the Information tab as shown below.

Visualise the data returns

As results are found they may also be displayed graphically in two different visualisations based on navigable clusters of nodes. For the "Radial" view (see below) a 'click of the mouse (left button)' is needed to browse up and down the various nodes as follows:

              all images, catalogues, spectra, timed data
                                   |
                one of above only (see screenshot below)
                                   |
  offset in arcsecs or degrees (user may toggle) from centre of search region
                                   |
                 position on sky (sexagesimal or degrees)
                                   |
    image, spectrum or catalogue record including format (where available)

In the example above the user has selected the SDSS DR5 image collection. There are images available at 7 different offsets from the catalogued SIMBAD position for M101 within a 0.01 degree radius. Each of those positions is at the given RA and DEC shown in the next node. The next screenshot below shows the view on selecting the nearest match at an offset of 0.03157 degrees at the position (210.8067, 54.3795). If you hover your mouse on the node below this position a tooltip shows brief metadata provided by the data centre indicating an r band fits format image file is available at this position.

Note that if the user prefers to see offsets in arcseconds simply click on the Sexagesimal button and all offsets and coordinates for M101 will be shown in Sexagesimal format (rather than decimal degrees).

An alternative visualisation, the'Hyperbolic' view shown below, visualises the same results in a tree state where all the nodes described may be visible and a click of the mouse re-centers on a selected node within a tree. Note also the yellow colour of the resources that the user has selected with a double left click of the mouse - see next help item.

If a search is not complete it may be stopped at any time by toggling the "Halt/Search" button and the user may jump back to the top visualisation level as needed using the "Go to Top" button. This is independent of which visualisation is being used.

Selecting data resources

Select a particular record or group of records (as in hyperbolic view above) by double clicking the relevant node which will then turn all selected nodes yellow. Once selected records can then be saved to your VOSpace or local disk by left-clicking the "Download" icon under Process/Actions. Click the "Clear Selection" button to unselect again.

Explore/visualise/analyse selected data in VO tools

Going back to the tabular visualisation once more (screenshot below) we show an example of the selection of u,g,r,i and z band optical fits images in SDSS DR5 for M101. Use shift-select for a continuous group or CTL-select to select individual files. As these are all image files compatible with Aladin the relevant option to send the images for viewing in Aladin becomes available (assuming the tool has already been started) under Process/Actions. Clicking the icon then sends the images.

If you have started additional VO tools such as TopCat (for analysing catalogues or Vizier Tables) or SPLAT (for exploring spectra) you will be given the option of sending the selected file to the relevant tool icon under Process/Actions if catalogue or spectral files have been selected. Further help and notes on these VO tools is available from the Helper Applications page

The application icons available on selecting a service are highlighted in the "Notificaton" window to the bottom right of the All-VO scope window. In the example shown to the left here the TopCat icon is visible showing that this is connected. Start the relevant VO tool needed and the icon will appear here also.

Note that simple or complex filtering and selection of sub samples within a catalogue can be highlighted in different colours when overlaid on images in the same region passed to Aladin! Or in reverse, clicking on a particular catalogue source overlaid on an image in Aladin will highlight that particular row entry in the TopCat table browser and/or highlight the point(s) in a 2-d plot of selected catalogue parameters made with TopCat. In the example shown below NED (blue) and SIMBAD (red) catalogued objects are overlaid on a DSS optical image for a well observed spiral galaxy.

Further details

See AstroScope Reference Help for further details of individual buttons and functionality.