Need advice on image processing pipeline

Hi Tom,

I got started using IDL because that is what San Francisco State encourages it's students to use.  A student license is $115 per year and a permanent license is $2,500.  The premanent license is expensive, but it is also cheap; depends on how much use you make of it.

I observe fast varying bright stars (~mag 6) and get between 1,000 and 1,600 images a night.  I've written a pipeline in IDL that allows me to throw all images into a single folder and push the buton, so to speak.  It reads the names and headers and sorts for filters, time of exposure, targets, calibrates and does aperture photometry.  I have a number of other procedures for inspecting the images, batch renaming of files, determining extinction coefficients, plotting orbital paramaters, and an embarassingly long list of other stuff that indicates entirely too much free time devoted to fooling around.

I'd be happy to share this stuff as it is pretty well generalized and the parts that aren't would be easy to fix.  Also IDL comes with the ability to export compiled programs and provides a free engine to run them.

I should mention that some of the professors at SFSU have IDL available but nevertheless do thier work using IRAF inside a Python wrapper and are very happy with that.  But those guys are more than smart and do this stuff for a living.  Comparatively, IDL is dead easy, equally powerful as IRAF, and intuitive - particlarly if you've ever written any Fortran code.  One thing I really like about IDL is that the code is completely transparent.  No black boxes.

Ben Davies

Hi Tom,

First, I can confirm what Ben said above: IDL is a nice software package, and the Astrolib package is a nice tool. I can also confirm that it's exhorbitantly expensive.  The AAVSO Chart Plotter used to be written in IDL -- one of the reasons we contracted Clockwork to write a new VSP in PHP was because of the licensing cost.  You might be able to compile Astrolib with GDL: http://gnudatalanguage.sourceforge.net/

Another possible no-cost alternative is CFITSIO, and in particular the Perl interface for it.  Perl makes file-handling incredibly easy, and once you learn FITSIO you should be able to do *basic* file processing (e.g. anything that involves arithmetic operations on whole frames like flatting and bias/dark subtraction) easily enough.

Honestly, IRAF isn't terribly hard for basic operations either.  Where IRAF starts to get difficult is in doing automated photometry (like DAOPHOT) or spectrum reductions.  Basic operations like flat-fielding and image combinations are straightforward.  And for Macintosh at least (and I assume Linux now) IRAF installation isn't anywhere near the agony it used to be.