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#### A.10.1.3 Display HiPS Cutout

Configuration for Display HiPS Cutout action

The Display HiPS Cutout action uses the hips2fits service at CDS to acquire a resampled image at the activated row's sky (or planetary) position and displays it in a no-frills image viewer window. The data is taken from a Hierarchical Progressive Survey (HiPS), an all-sky image data set. There are several hundred HiPS available providing imagery for many important sky and planetary survey datasets, so this easy to use activation action is often a good option for viewing imagery associated with activated positions.

Configuration:

RA Column
Dec Column
  Identifies the table columns representing coordinates. For sky data, these are in ICRS, but in the case of planetary data they just represent longitude and latitude.
Field of View
  Gives the angular size of the cutout on the sky. In most cases this will be a fixed value such as 1 degree or 45 arcsec, but you can choose a table expression instead, for instance the name of a column giving the source radius.
HiPS Survey
  Selects the survey from which the cutout is taken. The Select button on the right opens a menu with a hierarchical list of available surveys, including numerous sky and planetary/solar system object datasets. A little icon is displayed next to each survey in the menu indicating fractional sky coverage - a filled in ellipse indicates that the whole sky (or planet) is covered. If a HiPS has been selected from the menu, its full identifier and coverage icon is displayed below the entry field; hovering over these with the mouse gives a bit more information. It is also possible to type the full or partial survey name directly into the entry field.
Size in Pixels
  The width of the acquired image in pixels. The image is square, so this is also its height.

Alternatives: The hips2fits service is very flexible. If this action doesn't invoke it in exactly the way you want it to, you can customise the behaviour by using the Display Image action instead constructing your own custom hips2fits URL, perhaps by using the `hips2fitsUrl` function from the URLs class. You can also use the Send HiPS Cutout action if you want to view the image in an external viewer such as Aladin or ds9. If you want to be able to zoom around the HiPS image however, the best thing might be to open the HiPS in Aladin and use the Send Sky Coordinates action to communicate with it.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk