uk.ac.starlink.ast
Class SpecFrame

java.lang.Object
  extended by uk.ac.starlink.ast.AstObject
      extended by uk.ac.starlink.ast.Mapping
          extended by uk.ac.starlink.ast.Frame
              extended by uk.ac.starlink.ast.SpecFrame
Direct Known Subclasses:
DSBSpecFrame

public class SpecFrame
extends Frame

Java interface to the AST SpecFrame class - spectral coordinate system description. A SpecFrame is a specialised form of one-dimensional Frame which represents various coordinate systems used to describe positions within an electro-magnetic spectrum. The particular coordinate system to be used is specified by setting the SpecFrame's System attribute (the default is wavelength) qualified, as necessary, by other attributes such as the rest frequency, the standard of rest, the epoch of observation, units, etc (see the description of the System attribute for details).

By setting a value for thr SpecOrigin attribute, a SpecFrame can be made to represent offsets from a given spectral position, rather than absolute spectral values.

Licence

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public Licence as published by the Free Software Foundation; either version 2 of the Licence, or (at your option) any later version.

This program is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public Licence for more details.

You should have received a copy of the GNU General Public Licence along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street,Fifth Floor, Boston, MA 02110-1301, USA

See Also:
AST SpecFrame

Nested Class Summary
 
Nested classes/interfaces inherited from class uk.ac.starlink.ast.Mapping
Mapping.Interpolator, Mapping.Spreader
 
Field Summary
 
Fields inherited from class uk.ac.starlink.ast.Mapping
LINEAR_INTERPOLATOR, LINEAR_SPREADER, NEAREST_INTERPOLATOR, NEAREST_SPREADER
 
Fields inherited from class uk.ac.starlink.ast.AstObject
AST__BAD, AST__TUNULL, pointer
 
Constructor Summary
SpecFrame()
          Creates a SpecFrame.
 
Method Summary
 String getAlignStdOfRest()
          Get standard of rest to use when aligning SpecFrames.
 String getGeoLat()
          Synonym for Frame.getObsLat().
 String getGeoLon()
          Synonym for Frame.getObsLon().
 String getRefDec()
          Get the declination of the reference point.
 double[] getRefPos(SkyFrame frm)
          Return the reference position in a specified celestial coordinate system.
 String getRefRA()
          Get the right ascension of the reference point.
 double getRestFreq()
          Get the rest frequency.
 String getSourceSys()
          Get spectral system in which the source velocity is stored.
 double getSourceVel()
          Get the source velocity.
 double getSourceVRF()
          Get rest frame in which the source velocity is stored.
 String getStdOfRest()
          Get standard of rest.
 void setAlignStdOfRest(String alignStdOfRest)
          Set standard of rest to use when aligning SpecFrames.
 void setGeoLat(String geoLat)
          Synonym for Frame.setObsLat(java.lang.String).
 void setGeoLon(String geoLon)
          Synonym for Frame.setObsLon(java.lang.String).
 void setRefDec(String refDec)
          Set the declination of the reference point.
 void setRefPos(SkyFrame frm, double lon, double lat)
          Set the reference position in a specified celestial coordinate system.
 void setRefRA(String refRA)
          Set the right ascension of the reference point.
 void setRestFreq(double restFreq)
          Set the rest frequency.
 void setRestFreq(String restFreq)
          Sets the value of the restFreq attribute optionally with a unit string.
 void setSourceSys(String sourceSys)
          Set spectral system in which the source velocity is stored.
 void setSourceVel(double sourceVel)
          Set the source velocity.
 void setSourceVRF(double sourceVRF)
          Set rest frame in which the source velocity is stored.
 void setStdOfRest(String stdOfRest)
          Set standard of rest.
 
Methods inherited from class uk.ac.starlink.ast.Frame
angle, axAngle, axDistance, axOffset, convert, distance, findFrame, format, getActiveUnit, getAlignSystem, getBottom, getDigits, getDigits, getDirection, getDomain, getDut1, getEpoch, getFormat, getLabel, getMatchEnd, getMaxAxes, getMinAxes, getNaxes, getNormUnit, getObsLat, getObsLon, getPermute, getPreserveAxes, getSymbol, getSystem, getTitle, getTop, getUnit, intersect, norm, offset, offset2, permAxes, pickAxes, resolve, setActiveUnit, setAlignSystem, setBottom, setDigits, setDigits, setDirection, setDomain, setDut1, setEpoch, setEpoch, setFormat, setLabel, setMatchEnd, setMaxAxes, setMinAxes, setObsLat, setObsLon, setPermute, setPreserveAxes, setSymbol, setSystem, setTitle, setTop, setUnit, unformat
 
Methods inherited from class uk.ac.starlink.ast.Mapping
decompose, getInvert, getNin, getNout, getReport, getTranForward, getTranInverse, invert, linearApprox, mapBox, mapSplit, rate, rebin, rebinD, rebinF, rebinI, resample, resampleB, resampleD, resampleF, resampleI, resampleL, resampleS, setInvert, setReport, simplify, tran1, tran2, tranGrid, tranN, tranP
 
Methods inherited from class uk.ac.starlink.ast.AstObject
annul, clear, copy, delete, equals, finalize, getAstConstantI, getB, getC, getD, getF, getI, getID, getIdent, getL, getNobject, getObjSize, getRefCount, hashCode, isThreaded, reportVersions, sameObject, set, setB, setC, setD, setF, setI, setID, setIdent, setL, show, test, tune
 
Methods inherited from class java.lang.Object
clone, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

SpecFrame

public SpecFrame()
Creates a SpecFrame.

Throws:
AstException - if an error occurred in the AST library
Method Detail

getRefPos

public double[] getRefPos(SkyFrame frm)
Return the reference position in a specified celestial coordinate system. This function returns the reference position (specified by attributes RefRA and RefDec) converted to the celestial coordinate system represented by a supplied SkyFrame. The celestial longitude and latitude values are returned in radians.

Notes


- Values of AST__BAD will be returned if this function is invoked with the AST error status set, or if it should fail for any reason.

Parameters:
frm - Pointer to the SkyFrame which defines the required celestial coordinate system. If NULL is supplied, then the longitude and latitude values are returned as FK5 J2000 RA and Dec values.
Returns:
a 2-element array giving the (longitude,latitude) in radians of the reference point, in the coordinate frame represented by frm
Throws:
AstException - if an error occurred in the AST library

setRefPos

public void setRefPos(SkyFrame frm,
                      double lon,
                      double lat)
Set the reference position in a specified celestial coordinate system. This function sets the reference position (see attributes RefRA and RefDec) using axis values (in radians) supplied within the celestial coordinate system represented by a supplied SkyFrame.

Parameters:
frm - Pointer to the SkyFrame which defines the celestial coordinate system in which the longitude and latitude values are supplied. If NULL is supplied, then the supplied longitude and latitude values are assumed to be FK5 J2000 RA and Dec values.
lon - The longitude of the reference point, in the coordinate system represented by the supplied SkyFrame (radians).
lat - The latitude of the reference point, in the coordinate system represented by the supplied SkyFrame (radians).
Throws:
AstException - if an error occurred in the AST library

getAlignStdOfRest

public String getAlignStdOfRest()
Get standard of rest to use when aligning SpecFrames. This attribute controls how a SpecFrame behaves when it is used (by astFindFrame or astConvert) as a template to match another (target) SpecFrame. It identifies the standard of rest in which alignment is to occur. See the StdOfRest attribute for a desription of the values which may be assigned to this attribute. The default AlignStdOfRest value is "Helio" (heliographic).

When astFindFrame or astConvert is used on two SpecFrames (potentially describing different spectral coordinate systems), it returns a Mapping which can be used to transform a position in one SpecFrame into the corresponding position in the other. The Mapping is made up of the following steps in the indicated order:


- Map values from the system used by the target (wavelength, apparent radial velocity, etc) to the system specified by the AlignSystem attribute, using the target's rest frequency if necessary.


- Map these values from the target's standard of rest to the standard of rest specified by the AlignStdOfRest attribute, using the Epoch, ObsLat, ObsLon, ObsAlt, RefDec and RefRA attributes of the target to define the two standards of rest.


- Map these values from the standard of rest specified by the AlignStdOfRest attribute, to the template's standard of rest, using the Epoch, ObsLat, ObsLon, ObsAlt, RefDec and RefRA attributes of the template to define the two standards of rest.


- Map these values from the system specified by the AlignSystem attribute, to the system used by the template, using the template's rest frequency if necessary.

Returns:
this object's AlignStdOfRest attribute

setAlignStdOfRest

public void setAlignStdOfRest(String alignStdOfRest)
Set standard of rest to use when aligning SpecFrames. This attribute controls how a SpecFrame behaves when it is used (by astFindFrame or astConvert) as a template to match another (target) SpecFrame. It identifies the standard of rest in which alignment is to occur. See the StdOfRest attribute for a desription of the values which may be assigned to this attribute. The default AlignStdOfRest value is "Helio" (heliographic).

When astFindFrame or astConvert is used on two SpecFrames (potentially describing different spectral coordinate systems), it returns a Mapping which can be used to transform a position in one SpecFrame into the corresponding position in the other. The Mapping is made up of the following steps in the indicated order:


- Map values from the system used by the target (wavelength, apparent radial velocity, etc) to the system specified by the AlignSystem attribute, using the target's rest frequency if necessary.


- Map these values from the target's standard of rest to the standard of rest specified by the AlignStdOfRest attribute, using the Epoch, ObsLat, ObsLon, ObsAlt, RefDec and RefRA attributes of the target to define the two standards of rest.


- Map these values from the standard of rest specified by the AlignStdOfRest attribute, to the template's standard of rest, using the Epoch, ObsLat, ObsLon, ObsAlt, RefDec and RefRA attributes of the template to define the two standards of rest.


- Map these values from the system specified by the AlignSystem attribute, to the system used by the template, using the template's rest frequency if necessary.

Parameters:
alignStdOfRest - the AlignStdOfRest attribute of this object

getRefDec

public String getRefDec()
Get the declination of the reference point. This attribute specifies the FK5 J2000.0 declination of a reference point on the sky. See the description of attribute RefRA for details. The default RefDec is "0:0:0".

Returns:
this object's RefDec attribute

setRefDec

public void setRefDec(String refDec)
Set the declination of the reference point. This attribute specifies the FK5 J2000.0 declination of a reference point on the sky. See the description of attribute RefRA for details. The default RefDec is "0:0:0".

Parameters:
refDec - the RefDec attribute of this object

getRefRA

public String getRefRA()
Get the right ascension of the reference point. This attribute, together with the RefDec attribute, specifies the FK5 J2000.0 coordinates of a reference point on the sky. For 1-dimensional spectra, this should normally be the position of the source. For spectral data with spatial coverage (spectral cubes, etc), this should be close to centre of the spatial coverage. It is used to define the correction for Doppler shift to be applied when using the astFindFrame or astConvert method to convert between different standards of rest.

The SpecFrame class assumes this velocity correction is spatially invariant. If a single SpecFrame is used (for instance, as a component of a CmpFrame) to describe spectral values at different points on the sky, then it is assumes that the doppler shift at any spatial position is the same as at the reference position. The maximum velocity error introduced by this assumption is of the order of V*SIN(FOV), where FOV is the angular field of view, and V is the relative velocity of the two standards of rest. As an example, when correcting from the observers rest frame (i.e. the topocentric rest frame) to the kinematic local standard of rest the maximum value of V is about 20 km/s, so for 5 arc-minute field of view the maximum velocity error introduced by the correction will be about 0.03 km/s. As another example, the maximum error when correcting from the observers rest frame to the local group is about 5 km/s over a 1 degree field of view.

The RefRA and RefDec attributes are stored internally in radians, but are converted to and from a string for access. The format "hh:mm:ss.ss" is used for RefRA, and "dd:mm:ss.s" is used for RefDec. The methods astSetRefPos and astGetRefPos may be used to access the values of these attributes directly as unformatted values in radians.

The default for RefRA is "0:0:0".

Returns:
this object's RefRA attribute

setRefRA

public void setRefRA(String refRA)
Set the right ascension of the reference point. This attribute, together with the RefDec attribute, specifies the FK5 J2000.0 coordinates of a reference point on the sky. For 1-dimensional spectra, this should normally be the position of the source. For spectral data with spatial coverage (spectral cubes, etc), this should be close to centre of the spatial coverage. It is used to define the correction for Doppler shift to be applied when using the astFindFrame or astConvert method to convert between different standards of rest.

The SpecFrame class assumes this velocity correction is spatially invariant. If a single SpecFrame is used (for instance, as a component of a CmpFrame) to describe spectral values at different points on the sky, then it is assumes that the doppler shift at any spatial position is the same as at the reference position. The maximum velocity error introduced by this assumption is of the order of V*SIN(FOV), where FOV is the angular field of view, and V is the relative velocity of the two standards of rest. As an example, when correcting from the observers rest frame (i.e. the topocentric rest frame) to the kinematic local standard of rest the maximum value of V is about 20 km/s, so for 5 arc-minute field of view the maximum velocity error introduced by the correction will be about 0.03 km/s. As another example, the maximum error when correcting from the observers rest frame to the local group is about 5 km/s over a 1 degree field of view.

The RefRA and RefDec attributes are stored internally in radians, but are converted to and from a string for access. The format "hh:mm:ss.ss" is used for RefRA, and "dd:mm:ss.s" is used for RefDec. The methods astSetRefPos and astGetRefPos may be used to access the values of these attributes directly as unformatted values in radians.

The default for RefRA is "0:0:0".

Parameters:
refRA - the RefRA attribute of this object

getRestFreq

public double getRestFreq()
Get the rest frequency.

This attribute specifies the frequency corresponding to zero velocity. It is used when converting between velocity-based coordinate systems and other coordinate systems (such as frequency, wavelength, energy). The units are GHz. The default value is 1.0E5 GHz.

Returns:
this object's RestFreq attribute

setRestFreq

public void setRestFreq(double restFreq)
Set the rest frequency.

This attribute specifies the frequency corresponding to zero velocity. It is used when converting between velocity-based coordinate systems and other coordinate systems (such as frequency, wavelength, energy). The units are GHz. The default value is 1.0E5 GHz.

Parameters:
restFreq - the RestFreq attribute of this object

setRestFreq

public void setRestFreq(String restFreq)
Sets the value of the restFreq attribute optionally with a unit string. This attribute specifies the frequency corresponding to zero velocity. It is used when converting between between velocity-based coordinate systems and and other coordinate systems (such as frequency, wavelength, energy, etc). The default value is 1.0E5 GHz.

When setting a new value for this attribute, the new value can be supplied either directly as a frequency, or indirectly as a wavelength or energy, in which case the supplied value is converted to a frequency before being stored. The nature of the supplied value is indicated by appending text to the end of the numerical value indicating the units in which the value is supplied. If the units are not specified, then the supplied value is assumed to be a frequency in units of GHz. If the supplied unit is a unit of frequency, the supplied value is assumed to be a frequency in the given units. If the supplied unit is a unit of length, the supplied value is assumed to be a (vacuum) wavelength. If the supplied unit is a unit of energy, the supplied value is assumed to be an energy. For instance, the following strings all result in a rest frequency of around 1.4E14 Hz being used: "1.4E5", "1.4E14 Hz", "1.4E14 s**-1", "1.4E5 GHz", "2.14E-6 m", "21400 Angstrom", "9.28E-20 J", "9.28E-13 erg", "0.58 eV", etc.

When getting the value of this attribute, the returned value is always a frequency in units of GHz.

Parameters:
restFreq - a string representing the new restFreq value

setGeoLat

public void setGeoLat(String geoLat)
Synonym for Frame.setObsLat(java.lang.String).


getGeoLat

public String getGeoLat()
Synonym for Frame.getObsLat().


setGeoLon

public void setGeoLon(String geoLon)
Synonym for Frame.setObsLon(java.lang.String).


getGeoLon

public String getGeoLon()
Synonym for Frame.getObsLon().


getSourceSys

public String getSourceSys()
Get spectral system in which the source velocity is stored. This attribute identifies the spectral system in which the SourceVel attribute value (the source velocity) is supplied and returned. It can be one of the following:

- "VRAD" or "VRADIO": Radio velocity (km/s) - "VOPT" or "VOPTICAL": Optical velocity (km/s) - "ZOPT" or "REDSHIFT": Redshift (dimensionless) - "BETA": Beta factor (dimensionless) - "VELO" or "VREL": Apparent radial ("relativistic") velocity (km/s)

When setting a new value for the SourceVel attribute, the source velocity should be supplied in the spectral system indicated by this attribute. Likewise, when getting the value of the SourceVel attribute, the velocity will be returned in this spectral system.

If the value of SourceSys is changed, the value stored for SourceVel will be converted from the old to the new spectral systems.

The default value is "VELO" (apparent radial velocity).

Returns:
this object's SourceSys attribute

setSourceSys

public void setSourceSys(String sourceSys)
Set spectral system in which the source velocity is stored. This attribute identifies the spectral system in which the SourceVel attribute value (the source velocity) is supplied and returned. It can be one of the following:

- "VRAD" or "VRADIO": Radio velocity (km/s) - "VOPT" or "VOPTICAL": Optical velocity (km/s) - "ZOPT" or "REDSHIFT": Redshift (dimensionless) - "BETA": Beta factor (dimensionless) - "VELO" or "VREL": Apparent radial ("relativistic") velocity (km/s)

When setting a new value for the SourceVel attribute, the source velocity should be supplied in the spectral system indicated by this attribute. Likewise, when getting the value of the SourceVel attribute, the velocity will be returned in this spectral system.

If the value of SourceSys is changed, the value stored for SourceVel will be converted from the old to the new spectral systems.

The default value is "VELO" (apparent radial velocity).

Parameters:
sourceSys - the SourceSys attribute of this object

getSourceVel

public double getSourceVel()
Get the source velocity. This attribute (together with SourceSys, SourceVRF, RefRA and RefDec) defines the "Source" standard of rest (see attribute StdOfRest). This is a rest frame which is moving towards the position given by RefRA and RefDec at a velocity given by SourceVel. A positive value means the source is moving away from the observer. When a new value is assigned to this attribute, the supplied value is assumed to refer to the spectral system specified by the SourceSys attribute. For instance, the SourceVel value may be supplied as a radio velocity, a redshift, a beta factor, etc. Similarly, when the current value of the SourceVel attribute is obtained, the returned value will refer to the spectral system specified by the SourceSys value. If the SourceSys value is changed, any value previously stored for the SourceVel attribute will be changed automatically from the old spectral system to the new spectral system.

When setting a value for SourceVel, the value should be supplied in the rest frame specified by the SourceVRF attribute. Likewise, when getting the value of SourceVel, it will be returned in the rest frame specified by the SourceVRF attribute.

The default SourceVel value is zero.

Notes


- It is important to set an appropriate value for SourceVRF and SourceSys before setting a value for SourceVel. If a new value is later set for SourceVRF or SourceSys, the value stored for SourceVel will simultaneously be changed to the new standard of rest or spectral system.

Returns:
this object's SourceVel attribute

setSourceVel

public void setSourceVel(double sourceVel)
Set the source velocity. This attribute (together with SourceSys, SourceVRF, RefRA and RefDec) defines the "Source" standard of rest (see attribute StdOfRest). This is a rest frame which is moving towards the position given by RefRA and RefDec at a velocity given by SourceVel. A positive value means the source is moving away from the observer. When a new value is assigned to this attribute, the supplied value is assumed to refer to the spectral system specified by the SourceSys attribute. For instance, the SourceVel value may be supplied as a radio velocity, a redshift, a beta factor, etc. Similarly, when the current value of the SourceVel attribute is obtained, the returned value will refer to the spectral system specified by the SourceSys value. If the SourceSys value is changed, any value previously stored for the SourceVel attribute will be changed automatically from the old spectral system to the new spectral system.

When setting a value for SourceVel, the value should be supplied in the rest frame specified by the SourceVRF attribute. Likewise, when getting the value of SourceVel, it will be returned in the rest frame specified by the SourceVRF attribute.

The default SourceVel value is zero.

Notes


- It is important to set an appropriate value for SourceVRF and SourceSys before setting a value for SourceVel. If a new value is later set for SourceVRF or SourceSys, the value stored for SourceVel will simultaneously be changed to the new standard of rest or spectral system.

Parameters:
sourceVel - the SourceVel attribute of this object

getSourceVRF

public double getSourceVRF()
Get rest frame in which the source velocity is stored. This attribute identifies the rest frame in which the source velocity or redshift is stored (the source velocity or redshift is accessed using attribute SourceVel). When setting a new value for the SourceVel attribute, the source velocity or redshift should be supplied in the rest frame indicated by this attribute. Likewise, when getting the value of the SourceVel attribute, the velocity or redshift will be returned in this rest frame.

If the value of SourceVRF is changed, the value stored for SourceVel will be converted from the old to the new rest frame.

The values which can be supplied are the same as for the StdOfRest attribute (except that SourceVRF cannot be set to "Source"). The default value is "Helio".

Returns:
this object's SourceVRF attribute

setSourceVRF

public void setSourceVRF(double sourceVRF)
Set rest frame in which the source velocity is stored. This attribute identifies the rest frame in which the source velocity or redshift is stored (the source velocity or redshift is accessed using attribute SourceVel). When setting a new value for the SourceVel attribute, the source velocity or redshift should be supplied in the rest frame indicated by this attribute. Likewise, when getting the value of the SourceVel attribute, the velocity or redshift will be returned in this rest frame.

If the value of SourceVRF is changed, the value stored for SourceVel will be converted from the old to the new rest frame.

The values which can be supplied are the same as for the StdOfRest attribute (except that SourceVRF cannot be set to "Source"). The default value is "Helio".

Parameters:
sourceVRF - the SourceVRF attribute of this object

getStdOfRest

public String getStdOfRest()
Get standard of rest. This attribute identifies the standard of rest to which the spectral axis values of a SpecFrame refer, and may take any of the values listed in the "Standards of Rest" section (below).

The default StdOfRest value is "Helio".

Standards of Rest

The SpecFrame class supports the following StdOfRest values (all are case-insensitive):


- "Topocentric", "Topocent" or "Topo": The observers rest-frame (assumed to be on the surface of the earth). Spectra recorded in this standard of rest suffer a Doppler shift which varies over the course of a day because of the rotation of the observer around the axis of the earth. This standard of rest must be qualified using the ObsLat, ObsLon, ObsAlt, Epoch, RefRA and RefDec attributes.


- "Geocentric", "Geocentr" or "Geo": The rest-frame of the earth centre. Spectra recorded in this standard of rest suffer a Doppler shift which varies over the course of a year because of the rotation of the earth around the Sun. This standard of rest must be qualified using the Epoch, RefRA and RefDec attributes.


- "Barycentric", "Barycent" or "Bary": The rest-frame of the solar-system barycentre. Spectra recorded in this standard of rest suffer a Doppler shift which depends both on the velocity of the Sun through the Local Standard of Rest, and on the movement of the planets through the solar system. This standard of rest must be qualified using the Epoch, RefRA and RefDec attributes.


- "Heliocentric", "Heliocen" or "Helio": The rest-frame of the Sun. Spectra recorded in this standard of rest suffer a Doppler shift which depends on the velocity of the Sun through the Local Standard of Rest. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "LSRK", "LSR": The rest-frame of the kinematical Local Standard of Rest. Spectra recorded in this standard of rest suffer a Doppler shift which depends on the velocity of the kinematical Local Standard of Rest through the galaxy. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "LSRD": The rest-frame of the dynamical Local Standard of Rest. Spectra recorded in this standard of rest suffer a Doppler shift which depends on the velocity of the dynamical Local Standard of Rest through the galaxy. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "Galactic", "Galactoc" or "Gal": The rest-frame of the galactic centre. Spectra recorded in this standard of rest suffer a Doppler shift which depends on the velocity of the galactic centre through the local group. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "Local_group", "Localgrp" or "LG": The rest-frame of the local group. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "Source", or "src": The rest-frame of the source. This standard of rest must be qualified using the RefRA, RefDec and SourceVel attributes.

Where more than one alternative System value is shown above, the first of these will be returned when an enquiry is made.

Returns:
this object's StdOfRest attribute

setStdOfRest

public void setStdOfRest(String stdOfRest)
Set standard of rest. This attribute identifies the standard of rest to which the spectral axis values of a SpecFrame refer, and may take any of the values listed in the "Standards of Rest" section (below).

The default StdOfRest value is "Helio".

Standards of Rest

The SpecFrame class supports the following StdOfRest values (all are case-insensitive):


- "Topocentric", "Topocent" or "Topo": The observers rest-frame (assumed to be on the surface of the earth). Spectra recorded in this standard of rest suffer a Doppler shift which varies over the course of a day because of the rotation of the observer around the axis of the earth. This standard of rest must be qualified using the ObsLat, ObsLon, ObsAlt, Epoch, RefRA and RefDec attributes.


- "Geocentric", "Geocentr" or "Geo": The rest-frame of the earth centre. Spectra recorded in this standard of rest suffer a Doppler shift which varies over the course of a year because of the rotation of the earth around the Sun. This standard of rest must be qualified using the Epoch, RefRA and RefDec attributes.


- "Barycentric", "Barycent" or "Bary": The rest-frame of the solar-system barycentre. Spectra recorded in this standard of rest suffer a Doppler shift which depends both on the velocity of the Sun through the Local Standard of Rest, and on the movement of the planets through the solar system. This standard of rest must be qualified using the Epoch, RefRA and RefDec attributes.


- "Heliocentric", "Heliocen" or "Helio": The rest-frame of the Sun. Spectra recorded in this standard of rest suffer a Doppler shift which depends on the velocity of the Sun through the Local Standard of Rest. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "LSRK", "LSR": The rest-frame of the kinematical Local Standard of Rest. Spectra recorded in this standard of rest suffer a Doppler shift which depends on the velocity of the kinematical Local Standard of Rest through the galaxy. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "LSRD": The rest-frame of the dynamical Local Standard of Rest. Spectra recorded in this standard of rest suffer a Doppler shift which depends on the velocity of the dynamical Local Standard of Rest through the galaxy. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "Galactic", "Galactoc" or "Gal": The rest-frame of the galactic centre. Spectra recorded in this standard of rest suffer a Doppler shift which depends on the velocity of the galactic centre through the local group. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "Local_group", "Localgrp" or "LG": The rest-frame of the local group. This standard of rest must be qualified using the RefRA and RefDec attributes.


- "Source", or "src": The rest-frame of the source. This standard of rest must be qualified using the RefRA, RefDec and SourceVel attributes.

Where more than one alternative System value is shown above, the first of these will be returned when an enquiry is made.

Parameters:
stdOfRest - the StdOfRest attribute of this object


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