On Tue, 30 Nov 2004, David Berry wrote:
> OK. I've been thinking about this for most of today. I don't think the
> concept of FluxFrame as a 1-D subclass of the Frame class representing
> a generic flux axis will work. In general you need more information
> than simply the flux value to convert between flux units - typically you
> also need the frequency (or wavelength etc) at which the flux value is
> measured.
>
> So my current plan would be to make FluxFrame 2-dimensional rather than
> 1-dimensional, and to make it a subclass of CmpFrame. So to create a
> FluxFrame you would supply the FluxFrame constructor with two 1-D Frames,
> the first would be a simple 1D Frame (with suitable units) and would
> represent the flux axis, and the second would be a SpecFrame and would
> represent the positional axis.
David,
seems you have come to much the same conclusions that I did -- except I
was thinking about if I could make some use a MathMap with flux and
spectral coordinates as input and modified flux as output -- so this must
be more-or-less what's required for spectra.
(Thinking ahead for a general system I guess you'd need to allow for other
Frames or SkyFrames as well as SpecFrames, the thought I had was that flux
can depend on azimuthal position, but that's not strictly a units
question).
> I presume the way it would work is that you would have access to a
> FluxFrame describing your currently displayed spectrum (the current Frame
> in your Plot?), and another FluxFrame describing the spectrum you wished
> to overlay. You would use astConvert to get the Mapping between them, and
> then add the new FluxFrame into your Plot using the Mapping returned by
> astConvert to connect it to the existing current Frame.
Good, sounds just like the usual manipulations.
Peter.
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