1.1.3.0 coordsys.restfrequency

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coordsys.restfrequency - Function

1.1.3 Recover the rest frequency

Description

If the Coordinate System contains a spectral coordinate, then it has a rest frequency. In fact, the spectral coordinate can hold several rest frequencies (to handle for example, an observation where the band covers many lines), although only one is active (for velocity conversions) at a time.

This function recovers the rest frequencies as a quantity vector. The first frequency is the active one.

You can change the rest frequencies with setrestfrequency.

If the Coordinate System does not contain a frequency coordinate, an exception is generated.

Arguments

Returns
record

Example

"""
#
print "\t----\t restfrequency Ex 1 \t----"
csys = cs.newcoordsys(spectral=T)
print csys.restfrequency()
#{’value’: [1420405751.7860003], ’unit’: ’Hz’}
csys.setrestfrequency (value=qa.quantity([1.2e9, 1.3e9],’Hz’), which=1, append=F)
print csys.restfrequency()
#{’value’: [1300000000.0, 1200000000.0], ’unit’: ’Hz’}
#
"""

In the example, the initial spectral coordinate has 1 rest frequency.
Then we set it with two, nominating the second as the active rest frequency,
and recover them.

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