SAOtng can display image data stored in IRAF image format, IRAF QPOE format, or standard FITS image format. The IRAF file types are recognized on the basis of their file extensions (.imh for IRAF images, .qp for QPOE). FITS files do not require a specific extension: they are recognized when the size of the file is an even multiple of 2880 bytes and when the SIMPLE keyword is found in the first 2880 bytes.
Section and filter extensions can be added to IRAF file names (e.g, "foo.qp[pha=4:7]"). Be aware, however, that the Unix shell requires such file specifications to be placed in quotes.
If a FITS image has a file size less than the number of bytes specified by the -maxsize switch (default: 4.1Mb), the entire file is read into memory. This speeds up sectioning operations considerably.
SAOtng is designed to support the display of other file types without program modification. Support for a new format requires 2 programs:
See Adding New File Formats to SAOtng for more information on adding new file types.