Wednesday, February 17, 2010

CASA guides

Hey! If you're learning CASA, check out this new collection of tips and tutorials that I've been contributing to:

And let me know if you see obvious holes in the documentation there (which is, clearly, still under development).

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Error in PCAL

Here's a question from Akshaya Rane:

I am doing polarization calibration and while trying to run 'pcal', I have encountered the following error. Does this has to do something with qualifiers?

PCAL 3: Purports to die of UNNATURAL causes

Any thoughts?

I should add that Eric Greisen says that if you spend an hour trying to figure out something in AIPS, and you can't, you should feel free to email him and ask his help.

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Thursday, February 4, 2010

AIPS to CASA cheat sheet

So, i've been spending the last couple days learning CASA, and I think the most intuitive way to think about it is in terms of what I would be doing in AIPS. Hence the below table. Most tasks in AIPS have a parallel in CASA, although it's not always a one-to-one transfer.

Update: New and improved as of March 5, 2010:

APROPOS taskhelp List tasks with a short description of their purposes
BLCAL blcal Calculate a baseline-based gain calibration solution
BLCHN blcal Calculate a baseline-based bandpass calibration solution
BPASS bandpass Calibrate bandpasses
CALIB gaincal Calibrate gains (amplitudes and phases)
CLCAL applycal Apply calibration to data
COMB immath Combine images
CPASS cpass Calibrate bandpasses by polynomial fitting
DBCON concat Concatenate ''u-v'' datasets
DEFAULT default Load a task with default parameters
FILLM importvla Import old-format VLA data
FITLD importuvfits Import a ''u-v'' dataset which is in FITS format
FITLD importfits Import an image which is in FITS format
FITTP exportuvfits Write a ''u-v'' dataset to FITS format
FITTP exportfits Write an image to FITS format
FRING --- Calibrate group delays and phase rates.
GETJY fluxscale Determine flux densities for other cals
GO go Run a task
HELP help Display the help page for a task
IMAGR clean Image and deconvolve
IMFIT imfit Fit gaussian components to an image
IMHEAD vishead View header for ''u-v'' data
IMHEAD imhead View header for an image
IMLIN imcontsub Subtract continuum in image plane
IMLOD importfits Import a FITS image
IMSTAT imstat Measure statistics on an image
INP inp View task parameters
JMFIT imfit Fit gaussian components to an image
LISTR listobs Print basic data
MCAT ls List image data files
MOMNT immoments Compute moments from an image
OHGEO imregrid Regrids an image onto another image's geometry
PBCOR immath Correct an image for the primary beam
PCAL polcal Calibrate polarization
POSSM plotcal Plot bandpass calibration tables
POSSM plotms Plot spectra
PRTAN listobs Print antenna locations
PRTAN plotants Plot antenna locations
QUACK flagdata Remove first integrations from scans
RENAME mv Rename an image or dataset
SETJY setjy Set flux densities for flux cals
SMOTH imsmooth Smooth an image
SNPLT plotcal Plot gain calibration tables
SPFLG viewer Flag raster image of time v. channel
SPLIT split Write out ''u-v'' files for individual sources
TASK inp Load a task with current parameters
TGET tget Load a task with parameters last used for that task
TVALL viewer Display image
TVFLG viewer Flag raster image of time v. baseline
UCAT ls List ''u-v'' data files
UVFIX fixvis Compute ''u'', ''v'', and ''w'' coordinates
UVFLG flagdata Flag data
UVLIN uvcontsub Subtract continuum from ''u-v'' data
UVLSF uvcontsub Subtract continuum from ''u-v'' data
UVPLT plotms Plot ''u-v'' data
UVSUB uvsub Subtracts model ''u-v'' data from corrected ''u-v'' data
WIPER plotms Plot and flag ''u-v'' data
ZAP rmtables Delete data files

Do you have a favorite AIPS-to-CASA pair? Disagree with any of the above? Let me know in the comments! I'm still learning.

p.s. I'm supposed to be writing CASA documentation for the beginner (e.g., myself), so I doubt this is the last time I will be seeking feedback.

p.p.s. Why is blogger putting this horrific space before my table? I can't get rid of it and it looks fine in the preview. quack. This tip seemed to get rid of it.

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Plot labels and tick marks

Reader René would like to know about some aesthetic issues in plotting:

I have a question regarding labeling. The LTYPE-parameter (eg. in task 'greys') lets you plot "Label in arcsec or other units from reference pixel". This is just what I need, but it stupidly plots it in degrees instead of arcminutes. Is there a way to change this? (Except transforming the coordinates of the whole image I mean ...)

Also is there a way to adjust the number of ticks to plot? (Add minor and major ticks?)

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