[fitsbits] Question(s) regarding development of proprietary FITS manipulation software. . .

[Rob Seaman]

Michael Williams writes:

> Why in the world are interpretive images even relevant?  Why would  
> *anyone* present FITS data as images if they are not image data?   
> Why not represent it as sound?

People have been "imaging" the sky since the camera (and film) were  
invented.  Galileo drew by hand what he saw through his telescope;  
Tycho and many earlier astronomers sketched what they had seen with  
their naked eyes.  FITS files are often presented as pictures because  
people think of the heavens that way.  The movie "Contact", however,  
offers one example of astronomical data presented, as you suggest, as  
sound.  The presentation of other data objects that can be  
represented with FITS - say spectra, time series, or catalogs - may  
indeed require the skills of Edward Tufte more than Eadweard  
Muybridge or Edward Elgar.

Astronomical data are rich in implications - the birth of the  
universe, the death of the stars, their rebirth in the heavy elements  
that make life and this computer possible.  The representation of  
rich data requires dense display techniques.  Astronomers look at  
data as pictures because contour maps and line plots can hide the  
lurking science.

The sky is also just plain pretty on all scales we've looked to  
date.  Should presentation graphics only occur as some add-on step  
relying on GIFs and JPEGs, not FITS?

> I guess that's what I'm getting at.  What relevance does an image  
> have to actual FITS data if there is no "attached" image, and what  
> is the proper means by which to display said image?

Consider HTML - the content (from the server) is distinct from the  
presentation (left to the client).  Same with FITS.  The image is in  
the content, not the format - and, of course, in the eye of the  
beholder.

For the proper means, you might download a copy of Ximtool or DS9 to  
reverse engineer the common techniques, the representational language  
(perhaps start with "window and stretch") and the graphical tools  
(histogram vectors are more expressive than scalar gammas, for  
instance).

Rob Seaman
NOAO