3/7/05.
Chaps,
I'm not sure who's still reading this list, but here goes.
I recently had a message from Heinz Andernach ([log in to unmask]) asking
about using Skycat (and other software) for measuring ellipses from direct
images. I don't know much about Skycat (I just wrote some of the
documentation describing how it communicates with remote archives).
Can't GAIA also do this sort of thing? And there is Sextractor of
course. Though none of it runs on Windows presumably.
Anyway, maybe anyone with any firm suggestions could reply to Heinz
directly (though I'd appreciate seeing a copy of any reply).
An abridged version of Heinz's message (with some personal pleasantries
removed) follows.
> recently I saw your name on the web page of the Skycat software, so I felt
> to ask you a question. I'm having a summer student for only a few weeks
> who is not used to Unix and I don't want to create him additional problems.
> His project will be to measure the positions of several hundred brightest
> galaxies in Abell clusters (which are exlusively elliptical galaxies), and
> for this I installed on his laptop the FITSview and Aladin software
> (the latter to derive redshifts and names for these galaxies). Ideally I
> would also wish to derive sizes, position angles and ellipticities for
> these galaxies. Another student, during his BSc project, is already
> struggling to do this with IRAF's task "ellipse" which seems to be
> non-trivial, so I don't want to bother the other (only visiting student)
> with this, so I thought of Skycat which allows to use a box around the
> galaxy for 2D gaussian fitting (yielding semi-major a and semi-minor
> axes, b, from which one could derive ellipticity via e = 1 - b/a,
> although this is not necessarily the same as the ellipticity of the
> lowest-surface-brightness contour of the external part of the galaxy
> (which I'm actually interested in).
>
> So I'd have basically two questions:
> - can you confirm that Skycat is not available for windows ?
> - do you have any other suggestion for deriving the parameters
> of galaxies I mentioned above?
cheers,
Clive.
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Clive Davenhall.
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