On Wed, 22 Oct 2008, David Berry wrote:
> 2008/10/22 Mark Taylor <[log in to unmask]>:
> > David and/or Peter,
> >
> > if I attempt to load the attached spectrum into SPLAT, I get the following
> > pop-up error:
> >
> > uk.ac.starlink.splat.util.SplatException: uk.ac.starlink.ast.AstException:
> > AST: Error at line 406 in file AstObject.c.
> > astMatch(SpecFrame): Inappropriate units (Hz) specified for a wavelength
> > axis.
> > Unable to accommodate the attribute setting "Digits(1)=17". (AST__BADUN)
> >
> > Naively eyeballing the headers it looks to me like this has frequency
> > in Hz in column 1 which I'd have thought would be OK. However, I know
> > practically nothing about spectrum FITS headers etc, so I expect
> > there's an error of some sort in the data. Can you comment on what's
> > wrong and how it might get fixed?
>
> Not sure what splat does with this sort of data. It's possible that it
> does not set a specific value for the SpecFrame's "System" attribute, in
> which case it would default to wavelength. Peter??
That seems to be what's going on, the SpecFrame has a System of WAVE, but
has unit's of Hz, which is clearly wrong. I'll investigate further.
I presume this is failing because the remapping within the frameset isn't
possible? But why is that needed when I'm just changing the digits
attribute?
Peter.
Begin FrameSet # Set of inter-related coordinate systems
# Title = "Data count versus Wavelength" # Title of coordinate system
# Naxes = 2 # Number of coordinate axes
# Domain = "DATAPLOT" # Coordinate system domain
# Epoch = 2000 # Julian epoch of observation
# Lbl1 = "Wavelength" # Label for axis 1
# Lbl2 = "Data count" # Label for axis 2
# System = "Compound" # Coordinate system type
# Uni1 = "Hz" # Units for axis 1 (Hertz)
# Uni2 = "Jy" # Units for axis 2 (Jansky)
# Dig1 = 17 # Individual precision for axis 1
# Digits = 7 # Default formatting precision
# Fmt1 = "%1.17G" # Format specifier for axis 1
IsA Frame # Coordinate system description
Nframe = 2 # Number of Frames in FrameSet
# Base = 1 # Index of base Frame
Currnt = 2 # Index of current Frame
Lnk2 = 1 # Node 2 is derived from node 1
Frm1 = # Frame number 1
Begin Frame # Coordinate system description
# Title = "2-d coordinate system" # Title of coordinate system
Naxes = 2 # Number of coordinate axes
Domain = "GRID" # Coordinate system domain
# Lbl1 = "Axis 1" # Label for axis 1
# Lbl2 = "Axis 2" # Label for axis 2
Ax1 = # Axis number 1
Begin Axis # Coordinate axis
End Axis
Ax2 = # Axis number 2
Begin Axis # Coordinate axis
End Axis
End Frame
Frm2 = # Frame number 2
Begin SpecFluxFrame # Compound spectral/flux coordinate system description
# Title = "Data count versus Wavelength" # Title of coordinate system
# Naxes = 2 # Number of coordinate axes
Domain = "DATAPLOT" # Coordinate system domain
# Lbl1 = "Wavelength" # Label for axis 1
# Lbl2 = "Data count" # Label for axis 2
# Uni1 = "Hz" # Units for axis 1 (Hertz)
# Uni2 = "Jy" # Units for axis 2 (Jansky)
# Dig1 = 17 # Individual precision for axis 1
# Digits = 7 # Default formatting precision
# Fmt1 = "%1.17G" # Format specifier for axis 1
IsA Frame # Coordinate system description
FrameA = # First component Frame
Begin SpecFrame # Description of spectral coordinate system
Naxes = 1 # Number of coordinate axes
System = "WAVE" # Coordinate system type
Ax1 = # Axis number 1
Begin Axis # Coordinate axis
Unit = "Hz" # Axis units (Hertz)
Digits = 17 # Default formatting precision
End Axis
IsA Frame # Coordinate system description
UWave = "Hz" # Preferred units for wavelength
End SpecFrame
FrameB = # Second component Frame
Begin FluxFrame # Description of flux values
Naxes = 1 # Number of coordinate axes
Ax1 = # Axis number 1
Begin Axis # Coordinate axis
Label = "Data count" # Axis Label
Symbol = "Data" # Axis symbol
Unit = "Jy" # Axis units (Jansky)
End Axis
IsA Frame # Coordinate system description
UFlxdn = "Jy" # Preferred units for flux density
End FluxFrame
IsA CmpFrame # Compound coordinate system description
End SpecFluxFrame
Map2 = # Mapping between nodes 1 and 2
Begin UnitMap # Unit (null) Mapping
Nin = 2 # Number of input coordinates
IsA Mapping # Mapping between coordinate systems
End UnitMap
End FrameSet
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