Usage of findNull

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Given an amplitude on a scale of 0..1, and an angularDiameter in arcseconds, this function determines the corresponding radius of the Besinc function within the first null (in units of kilowavelength). This is the function that describes the visibility amplitude of a uniform disk (like a planet). If the wavelength (in mm) or frequency (in GHz) is given, then baseline value returned will be in units of meters. See also printBaselineAngularScale.


au.findNull(angularDiameter,amplitude=0, wavelength=None, frequency=None)


CASA <3>: au.findNull(1.0,frequency=300)
wavelength = 0.999308 mm
first null occurs at 251.401 meters
  Out[3]: 251.40095873783335

CASA <4>: au.findNull(1.0,frequency=300,amplitude=0.2)
wavelength = 0.999308 mm
amplitude is 0.2*peak at 202.172 meters
  Out[4]: 202.17203920965335

-- ToddHunter - 2013-02-07

This topic: ALMA > TWikiUsers > ToddHunter > CasaExtensions > FindNull
Topic revision: 2013-02-07, ToddHunter
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