Chandra X-Ray Observatory
Last modified: 28 June 2018

Why can I only see a subsection of the event file? Where are the rest of the data?

When ds9 loads an event file, it automatically bins it into an image for display.

The default is to create a 1024x1024 image, binned by 1, centered between the min and max limits of each axis. So for example, when loading an ACIS event file, ds9 will create a 1024x1024 pixel image, with ~0.492" pixels (binned by 1), centered at (x,y) = (4096.5,4096.5). The image in the pan widget only shows the 1024x1024 binned data.

To display a larger part of the dataset, users need to either increase the bin-size (ie bin by 2, 4, etc) or increase the image axis lengths (eg 2048, 4096, 8192). These are both options under the Bin menu. Users can make these changes permanent by changing their Preferences. Panning around the image (middle-click, or by going in to Edit then Pan mode) changes the center about which the data are binned.

The Zoom operations only apply to the subsection of the event file currently binned into an image.

When users load an image into ds9, it displays the full image.

Last modified: 28 June 2018
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