[AstroPy] [SciPy-user] FITS images with header-supplied axes?

humufr at yahoo.fr humufr at yahoo.fr
Tue Apr 1 10:41:02 EDT 2008


I just want to discuss about a problem that our python astronomer have and the 
answer from Perry is a very good example of it. There are too many projects 
which are doing exactly the same thing and essentially because nothing is 
centralized or worst, in the case of pywcs, not advertised. 

For example Perry told us about pywcs developped by STSCI (it was the first 
time I saw any reference to this project) but Adam spoke about 
astlib ( http://astlib.sourceforge.net/ ) which are different package with 
exactly the same goal and I did myself something similar (even if it was fast 
and dirtier).

I think it's time to try to identified the most important task that the 
astronomer are needing and try to centralized all the effort at the same 
place. The astropy mail list is probably a good start as the 
astropy.scipy.org website.

Perhaps we can start to identified the need and desiderata. We will have too  
many but that some most important or urgent must be identified. As example, 
we clearly needed the pywcs and thanks to STSCI we have it now. We also need 
a package to plot our data, images etc. Matplotlib is very good but does have 
a major problem (at least for my point of view), it's slow, very slow for big 
array or can't even produce the image if the image is too big. ( If I 
remember a precedent discussion, the problem is mainly due to Agg.)

After we need to know, if possible, for which project if someone is doing 
something, who and how to contact him/her. So interested people can 
eventually help him/her to do it. It's seems that STSCI is doing most of the 
work but I'm pretty sure that other people are willingly to help them to 
extend python to be the ideal tool for astronomer.

Just my 2 cents, 


Le Sunday 30 March 2008 10:54:04 Perry Greenfield, vous avez écrit :
> On Mar 28, 2008, at 8:28 PM, Keflavich wrote:
> > Is there any plotting routine in scipy / matplotlib that can plot a
> > fits image with correct WCS coordinates on the axes?  I know pyfits
> > can load fits files, astLib has routines to interpret header
> coordinates, and I think you can make the axes different using
> > matplotlib transforms, but is there anything that puts all three
> > together currently available?
> >
> > Thanks,
> > Adam
> Well, we (STScI) recently wrapped WCSLIB to obtain a mapping function
> between pixel and sky coordinates for python (you can find it as pywcs in
> astrolib on scipy; that may have been what you were referring to).
> But I'm not sure you understand what you are asking for with regard to
> matplotlib. The new transforms stuff should make it much easier to display
> the sky coordinates in the interactive display. The axis labeling is a
> different matter. Suppose your image (let's say it's 1Kx1K for the sake of
> discussion) is rotated 45 degrees with regard to north (either way, it
> doesn't really matter). What would you expect to see for axis labels? I
> don't think it is at all obvious how people would want labeling to be done
> along the edges of the image. I can imagine someone wanting axes or grids
> superimposed on the image itself, but that's not quite the same thing. Do
> you want the image rotated so that it is resampled on to RA and Dec and
> displayed that way?
> In any event, no we haven't yet done anything to try to integrate all three
> things. Among other things we wanted to make sure that the api for the wcs
> info was suitable before doing a lot with it (and in the meantime, Mike is
> working on rewriting drizzle which is taking a lot of his time).
> Perry
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