IDL

PSFs in IDL

Mar 18th

Two methods of approximating a point-spread function in IDL:

1. StarFinder seems to do a great job at finding point sources in crowded fields. It includes a routine for generating the Airy pattern. For a 51 x 51 array, with the peak at [25, 25], and an FWHM of 8.0 pixels, this is the command:

psf = airy_pattern(51, 51, 25, 25, 2./8.0)
isurface, psf

The output looks something like this:

PSF Airy pattern (StarFinder/IDL)

2. The IDL Astronomy User’s Library contains a routine, psf_gaussian, that produces a Gaussian PSF. To produce the same as above, the command would be:

psf = psf_gaussian(npix=51, fwhm=8.0, /double)
isurface, psf

… which produces something like this:

PSF Gaussian (IDL Astronomy User's Library)

IDL, point sources

The eclipse of IDL 7

Mar 3rd

Posted by Anthony in Computing

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I’ve finally made the transition from IDL 6.4 to IDL 7. Here are my handy hints…

IDL Workbench rocks! (This is because it is basically Eclipse, which is a proper development environment, unlike that hideous old IDLDE.)
Another reason for using IDL Workbench (for me at least, and for now) is that IDL help doesn’t seem to work if Java 6 is the default (as it is on my Mac), but the help does work if launched through the IDL Workbench.

To transition to IDL Workbench:

Import your code as described on David Fanning’s page – fret not, it’s easy and harmless
Preferences -> IDL -> Startup file, if you have one, and
Preferences -> IDL -> Paths -> Insert… for me it was just my idl folder, including all sub-folders, to mimic my $IDL_PATH environment variable.

IDL

pIDLy: IDL within Python

Jan 31st

Posted by Anthony in Computing

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Now Python and IDL can talk to each other (okay, Python talks to IDL and IDL does what it’s told), using pIDLy (pronounce as you please). I experimented with a few other solutions available online but couldn’t get them to work. So I cobbled this one together with surprisingly little trouble, thanks largely to pexpect.

IDL, Python

IDL code miscellany

Jan 28th

Posted by Anthony in Computing

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IDLdoc 3.0 (more info here) gives my badly-written bits of IDL the deceptive appearance of being well designed, useful and user-friendly. So I’ve made a few available here for your enjoyment.

IDL