NB: The use of PNG representation files is deprecated in favor of fits2fits large file support. See Dealing with Large Files for more information.
X-ray archives present special problems for displaying data. Instead of images pixels, X-ray data files consist of detected photons stored in FITS binary tables. These can be hundreds of megabytes in size, regardless of the image dimensions. Downloading (and then binning) these tables on the fly can be painfully slow.
To remedy this situation, JS9 supports a special PNG representation file, explicitly tied to the original FITS file. The idea is that you can create a representation image from the original FITS data and use that file for display in JS9, while still supporting server-side analysis using the original file.
Other benefits include:
See The PNG Representation File for more information.
|FITS binary tables (first three are compressed):||FITS files with dynamic fits2png conversion:|