Kvis & AIPS awesomeness!

You can use kvis to view your AIPS images directly! See below for more details. Thanks to Bryan Gaensler for this awesome tip.



The program kvis is an image viewer that is part of the karma image analysis package. An undocumented, but cool feature of this program is that if you navigate to your AIPS data directory (typically somewhere like $AIPS_ROOT/DATA/LOCALHOST_1) in the kvis file selector you will see each AIPS image file with its correct name (instead of crytic filenames like FQD001001.099;) and be able to click on them and view them. Once you've got then in kvis, you can even save to FITS.

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Missing Scans!

I'm reducing some EVLA-VLA data, and I discovered that one of the calibrator scans was missing in the data. It was listed in the "scan list" on the archive and the observe files were (to the best of our knowledge) correct. After emailing the analysts, we figured out that the scan was flagged by the online flagger. You can read in the data without applying these online flags using CPARM(3) = 16.

I'm still trying to figure out why it was flagged, and I'm assuming that this information is stored in the "OF Table" extension. However, I haven't been able to find any information on that table using google (googling "aips 'OF table'" doesn't really work because you get a lot of pages with properties of tables, not info about the OF table).

I'll post what I learn about this (if anything), but it's something to keep in mind if you find yourself missing scans..

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Multi-scale clean vs. regular clean

Those of you clean afficiandos should check out this recent astro-ph article:
Multi-Scale CLEAN: A comparison of its performance against classical CLEAN in galaxies using THINGS

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SUBIM question

A question from reader Jenny:

I'm trying to combine two optical images using AIPS (don't ask why!) but the FITS images I have are not centred on the sources I want to combine. I want to use SUBIM to create images centred on my targets but is there a way to get the task to create the image using the ra and dec of the target rather than TRC and BLC?

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Mystery Error: TASK HAS NOT BEGUN IN 15.1 SECONDS

A question from Tony:

Has anyone start getting the following error message:

AIPS 1: TASK HAS NOT BEGUN IN 15.1 SECONDS
AIPS 1: Begin check for any 'standard' scratch files
AIPS 1: Scratch files -- destroyed: 0 still active: 0
AIPS 1: Resumes

A few people across the department have receive the same error message, and I think it is a problem related to 31DEC08.

But why 15.1 seconds?!

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Imaging GMRT Data

A plea for advice from an anonymous reader:

Off topic, & quite possibly a stupid question from an AIPS newbie, but I'd really appreciate any help. I'm currently processing some GMRT data (30mins, 610MHz, 38 facets, each imsize 512, cellsize 1.5), & IMAGR seems to take a very long time to run, ~2hrs for 1000 iterations. I'm wondering if this is normal, or if something has gone wrong during the SPLAT process, where I split off the source from the multi source dataset, and averaged every 7 channels between channels 1 & 105.

IMAGR, with NCHAV=15,when running, appears to process channels 1-15, then 2-16,3-17 etc, is this normal for data that has been averaged as above?
Thanks.

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Importing AIPS images into IRAF

Here is a question from reader donkeypuncher:

I'd like to use IRAF to do some analysis on images produced in AIPS. Alas, I am unable to open in IRAF the FITS files output by AIPS (task FITTP). I get this simple, non-informative message when I attempt to use the IRAF task display:

ERROR: Cannot open image (IMAGE.FITS)

I'm guessing it's a format issue, because I have no problem loading in ds9. Any ideas?

BTW, I like the site, thanks for your contributions!

My guess at an answer can be found if you click below..

I think that IRAF needs and expects the '.fits' suffix to be in all small letters. Try changing your image name to 'image.fits' and see if that helps.
Also-- something else I've noticed is that optical software often freaks out at the small pixel values in AIPS images (For example, are your pixel values on the order 10^-3 to 10^-6?). Once you get your image into IRAF, you might want to try multiplying your entire image by some large constant, say a million, using imarith. This could potentially save you headaches.

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