From the category archives:

analysis

Fourier Transforms of Images in Python

by Jessica March 3, 2010

There are many applications for taking fourier transforms of images (noise filtering, searching for small structures in diffuse galaxies, etc.). I wanted to point out some of the python capabilities that I have found useful in my particular application, which is to calculate the power spectrum of an image (for later separation of the distribution [...]

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Fitting surface brightness profiles

by Jane Rigby December 14, 2009

It’s time for another session of, “Which tool do you use to accomplish a given astro-task, and why that tool?”  The topic:  fitting surface brightness profiles.  Two likely suspects:  the Archangel package, and iraf’s stsdas.analysis.isophote.  OK, go.

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Better ways to make large image mosaics?

by Kelle October 21, 2009

Given the useful responses to Jane’s question about spectral line analysis, here’s another query for the community. This one is about making large image mosaics and it comes from Adam Ginsburg, a grad student at the University of Colorado, Boulder.
I want to make a large-scale mosaic of the Galactic Plane covering 90-180 degrees x a [...]

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The Integral Field Spectroscopy Wiki

by Kelle October 19, 2009

Here’s a guest post from Mark Westmoquette at the University College London.

Do you currently work with, or are you thinking about applying for integral field unit (IFU) observations? If so, then the Integral Field Spectroscopy wiki is for you.
With IFS instruments installed on all the main optical telescope facilities around the world, it is likely [...]

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Spectral line analysis tools

by Jane Rigby October 2, 2009

This is an embarrassing post, but I’m going to forge ahead.  Time was, we used IRAF and we hated it, but what else was there?  Now, there are many choices, lots of them buggy and badly documented, some of them superb.
Say I have a one-dimensional, flux-calibrated, wavelength-calibrated spectrum.  (So, all the hard work of calibration [...]

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Hungry for Plots? Get some APLpy!

by Eli July 20, 2009

Today APLpy 0.9.3 is out! It is a Python plotting package made to generate publication-quality plots in multiple formats such as EPS, PDF, PS, PNG, and SVG.
APLpy was created by Thomas Robitaille and Eli Bressert, who come from a Fortran and IDL background. With Python’s ease of use, portability, and programming they decided to make [...]

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Deal with upper limits

by Jane Rigby May 29, 2009

Often we have datasets in which quantities are not detected.  Those upper limits contain information — the flux was definitely below X.  It turns out, there’s a rich statistical literature on how to consider both detections and upper limits.   Yet often astronomers don’t properly incorporate those upper limits in their analysis.
Fortunately, several authors have explained [...]

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