au.sfBeam(frequency, pixelsize=10, diameter=12.0, xSamplesPerBeam=5.0, ySamplesPerBeam=None, xSamplingArcsec=None, ySamplingArcsec=None, convsupport=-1, makeplot=False, m=0, taper=10.0, geometricMean=False, obscuration=0.75, cmult=1.0, coffset=0.0, xmult=1.0, alpha=1.0, testOption=False, minlevels=[0,0], truncate=True, img=None, row=None, column=None, stokes='XX', plotfile='', verbose=False, fwhmfactor=None, excludeBand3=True, excludeBand3Below=109.0)

- frequency: floating point number in GHz (no units) or a string with units
- pixelsize: floating point number in arcseconds (no units)
- diameter: the diameter of the single dish antenna in meters (no units)
- xSamplesPerBeam: the number of sampled points per telescope FWHM beam along the X axis
- ySamplesPerBeam: the number of sampled points per telescope FWHM beam along the Y axis
- xSamplingArcsec: if not None, then use this value instead of xSamplesPerBeam
- ySamplingArcsec: if not None, then use this value instead of ySamplesPerBeam
- makeplot: if True, then also generate a png
- convsupport: radius in pixels, default=-1 --> 3 pixels, meaning a support width of 7 points
- m: The value to pass as m and n to scipy.special.pro_ang1_cv (note that the m in VLA computing memo 156 denotes a different quantity, the support width)
- taper: the illumination taper (in dB) to pass to au.primaryBeamArcsec
- fwhmfactor: if specified, pass this to au.primaryBeamArcsec, overriding taper
- obscuration: diameter in m to pass to au.primaryBeamArcsec
- geometricMean: if True, then return only the geometric mean beamsize; otherwise, return minorAxis,majorAxis,geometricMean (if the sampling is provided in both axes)
- cmult, coffset, xmult: these are coefficients to use in computing: supportwidth = (convsupport*cmult + coffset), and the radius in arcsec at which the SF goes to zero (supportwidth*pixelsize*xmult)
- testOption: if set to True, this will attempt to emulate the method used in SDGrid.cc to establish the convFunc. The result is nearly identical (1:10000) to my original method.
- alpha: the exponent of the weighting function, i.e. (1-nu*nu)**alpha, which is 1 in casa
- minlevels: a list of fractional values (from 0..1) above which to perform 1D Gaussian fits on the estimated restoring beam
- truncate: only used if taper=0, sets whether to truncate the Airy at the first null
- img: if not none, then use a row or column from this image as the beam model
- row: the row of img to use as the starting beam profile model
- column: the column of img to use as the starting beam profile model
- stokes: 'XX','YY' which Stokes to use in the img
- excludeBand3: if True, then don't use Band 3 TICRA patterns below excludeBand3Below'
- excludeBand3Below: frequency in GHz below which to not use Band 3 patterns

- If only the X-axis sampling is given:
- the FWHM of the restoring beam
- the FWHM of a Gaussian fit to the restoring beam

- If both X and Y-axis sampling is given:
- If geometricMean=True:
- the FWHM of the predicted restoring beam
- the FWHM of a Gaussian fit to the predicted restoring beam

- If geometricMean=False:
- the minor axis of the restoring beam
- the major axis of the restoring beam
- the geometric mean of the restoring beam computed using findFWHM()
- the geometric mean of the FWHM of a Gaussian fit to the restoring beam

- If geometricMean=True:

CASA <3>: au.sfBeam(114.7,taper=10) Out[3]: (55.404693642322442, 55.386051861589472) CASA <16>: au.sfBeam(336.5,pixelsize=3,taper=10,xSamplingArcsec=3.5,ySamplingArcsec=5.7,makeplot=T) Plot left in sfBeam.png Out[16]: (18.577381915209678, 18.833994064946779, 18.705247946320004, 18.700396982924687)-- ToddHunter - 2013-07-02

- sfBeam.png:

- comparison of grdsf (from casa/aips) and scipy with a value tuned to match grdsf:

I | Attachment | Action | Size | Date | Who | Comment |
---|---|---|---|---|---|---|

png | fred_vs_scipy.png | manage | 52 K | 2013-11-15 - 14:08 | ToddHunter | comparison of grdsf (from casa/aips) and scipy with a value tuned to match grdsf |

png | sfBeam.png | manage | 81 K | 2013-11-15 - 14:05 | ToddHunter | created in au v1.1481 |

This topic: ALMA > TWikiUsers > ToddHunter > CasaExtensions > SfBeam

Topic revision: 2014-03-27, ToddHunter

Topic revision: 2014-03-27, ToddHunter

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