Testing My Radially Variable Spatial Filter Code

I think I need to update my blog; it has been so long since my last update… Also should I prove that I’m still alive here.

I saw a message in the comets-ml posted by Martino Nicolini that the PSI website has released a web tool for processing cometary images, including azimuthal median/average/renormalization filters, 1/rho coma model division, and, quite unfamiliar to me, radially variable spatial filter (http://www.psi.edu/research/cometimen). I attempted to process an image taken by HST regarding comet C/2012 S1 (ISON) in May 2013 with the online tool, however, I had difficulty in retrieving the enhanced or processed data. Weirdly the size of the to-be-downloaded file was always 0 KB, obviously problematic. With consideration that the network is not permanently available for me, it sounds absurd and waste-of-time for me to wait for accessible network before performing specially processed cometary images, and therefore I decided to write codes for my own purpose.

So I did by taking reference to the explanation file of the enhancement techniques, understanding the global idea of how the radially variable spatial filter works. Realizing the algorithm of the filter was proved easy, and it didn’t take me long to accomplish the IDL routine.

I did some tests with the image CometCIEF_test.fits provided in this page. The following was generated with kernel A = 4.0, B = 4.0, N = 0.4. It looks correct anyway, quite similar to the appearance in the tutorial file.

RVSF test imageHowever, I found my result would look somewhat different from those presented in the tutorial file if the kernel size was smaller — probably the scaling plays a role there, yet anyway my outcome would look less detailed. The corresponding FORTRAN source code of the filter in the PSI page seems to has a typo, which I have already reported to Padma Yanamandra-Fisher. I’m still comparing my codes against the PSI’s…

Testing My Radially Variable Spatial Filter Code

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