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

[Michael Williams]

Ok, I actually asked a follow-on question in another post/e-mail.   
Basically I asked if these astronomers images were literally live  
images (perhaps of the stars, or nieces and nephews), or if they were  
simply arbitrary graphical representations of data that had no  
reference in reality.  Also, given the fact that, as you said,  
reverse transformation isn't always possible, why in the world does  
it matter if the user can perform image manipulations of any type?  I  
mean, if there is no consistent way to produce an image, then why do  
we care?

Thanks,
Michael


On Aug 27, 2007, at 5:15 AM, Thierry Forveille wrote:

> gberz3 a écrit :
>> Why would *anyone* present FITS data as images if they are
>> not image data?  Why not represent it as sound?
>> 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?
> The issue is mostly your notion of an image, vs an astronomer's
> notion of the same. To you an image is something that can be
> univocally displayed on a screen or printed, while to
> astronomers it is a set of values (ideally in physical units,
> such as Watts per square meter per steradian) sampled on a
> regular grid. There is some link between the two notions,
> but not a unique one: an astronomer's image can be displayed
> but not in one unique way, and the reverse transformation
> if/when at all possible, requires additional information
> (e.g. the physical values for a subset of the pixels) and
> significant calibration work. Essentially, an astromer's
> image is a richer dataset, and someone needs to decide how
> to degrade that information to what a display can show.
>
> In addition, images (in the astronomer's definition) is only
> one of the data classes that can be stored in FITS.