> > 1 2 3 4 5 6 7 8 eight channels
> > | | | | | | | | |
> > -----------------
> > |----BANDPASS---|
> >
> > (here I use flux to include energy etc. and wavelength/frequency to
> > include freq., wavel., energy, wavenumber)
>
> Would this work if each channel was a separate Passband? We might have a
> Passband that was a collection of other Passbands (ie what you've labelled as
> BANDPASS above) to make it easier to use collections of them. I'll try and get
> some diagrams together on the page to make this clearer.
I think that would be overkill, at least in the (?majority?) of such cases where the channels are the same apart from a displacement along the wavelength (etc.) axis which is linear in the appropriate coordinate - usually you talk about the entire bandpass which may or may not be subdivided into n channels of x width... (or described by y Gaussian) where x or y are the same for the entire bandpass. There is then a sensitivity function F(n)
> > an uncertainty if we are e.g. using linear bandpasses only.
>
> Hmmm; what I meant was that assuming getPassrate(wavelength) returns a
> probability value between 0 and 1 (inc), will you want that probability
> value to have an associated error? Will you want to give an uncertain
> wavelength?
I think that is what I was trying to explain - let's be mathematical:
Bandpass has centre x metres which has uncertainty (due to reference wavelength standard) of deltax metres. Probably not an issue for much VO-accessible data at present but should be allowed to be added in future.
However did you mean:
If I ahve understood you, getPassrate(wavelength) is approximated by F(n)
>
> Let us say we are using shaped bandpasses - would you need an error on the band
> shape then?
In some cases the exact form of F(x) may not be known,
or the effective bandpass may depend on the source being observed e.g.
the x-ray case. So
leave room for errors - in fact as a general prnciple I would elave room
for errors in everything....
> >> - Is 'passrate(Fravergy)', returning a value 0-1 probability, sufficient for
> >>Radio, X-Ray, etc?
Ah - a continuous function [0,1] or even ]0,1[ :)
>
> No I actually meant:
>
> 1| xxx
> | x x
> 0.5| x x
> | x x
> 0 -----------------> Wavelength
>
> Which hopefully will clear up a lot of other comments you made! Will people
> want any other characteristic than probability of transmission?
Indeed, thanks very much!
cheers
Anita Received on 2004-06-01Z11:29:06