Standard of rest to use when aligning SpecFrames AlignStdOfRest
"
Helio"
(heliocentric).
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.