[iaufwg] FITS conventions

[Mark Calabretta]

On Tue 2006/02/14 11:22:04 BST, Lucio Chiappetti wrote
in a message to: IAU-FWG <iaufwg at nrao.edu>

>I do not feel at all the lack of a fixed or mandatory colour 
>representation for a standard (NAXIS=2) FITS image, since I can obtain 
>whatever look I want with a display program like ds9 (incidentally, after 
>having written in the past some homegrown stuff [not to talk of IHAP and 
>MIDAS], and done some use of IDL, I would say I've personally now settled 
>on almost exclusive use of ds9).

Since you mentioned ds9, here (appended) is what it does in the absence
of any formal FITS convention for representing colour, from the release
notes for version 3.0.

Mark Calabretta
ATNF

>>>

DS9 Version 3.0 New Features
----------------------------

RGB Images
----------
DS9 now supports RGB Images.  An RGB Image is an image which is composed of 3
color channels, red, green, and blue.  In each channel is loads a FITS image,
FITS binary table, or FITS Mosaic.  Each channel has its own Scale and Bin
parameters.  DS9 will align the images in the three channels base on the WCS,
Physical, or Image coordinates.  For more infomation, see File Menu, XPA, and
Command Line Options.

...

DS9 support two new file formats for RGB images.  The first is FITS Data Cube,
containing 3 slices which represent the red, green, and blue color channels.
The second, is a FITS Multiple Extension file, containing 3 extensions, again
representing the red, green, and blue color channels.  For more infomation,
please see File Formats.