phot.flux - an Addendum

[Frederic V. "Rick" Hessman]

> Don't want to step on any radio astronomer's toes, but flux density  
> is flux.    Yes, I know, it's monochromatic flux per unit  
> frequency, but where's the distinction between bolometric flux,  
> monochromatic flux per unit frequency, and monochromatic flux per  
> unit wavelength?  Do we also then have to support the use of  
> candela's, lux's, and the lot - also physical (even SI!) terms for  
> the same things?  How about (see, e.g., Mihalas):
>
>     phot.flux                      generic net rate of radiant  
> energy flow per unit area and time
>     phot.flux.freq              monochromatic flux per unit  
> frequency, flux density
>     phot.flux.wave           monochromatic flux per unit wavelength
>     phot.flux.bol                bolometric flux
>     phot.flux.Eddington   Eddington flux = flux / 4PI
>
> I was going to suggest adding  phot.flux.astr (that terrible factor  
> of PI or /1PI, depending upon how you look at it!), but I won't......

Sorry - should have re-read the 1.02 documentation: "flux density"  
has been generalized beyond it's normal use.  How do we then
distinguish between the many different forms?  By units alone, i.e.  
non-UCD things?  That works fine for things like lengths and times  
and masses, since the physical quantities are well defined beyond  
their units, but F_nu and F_lambda are totally different quantities  
and this fact is utterly independent of the units.

Perhaps

        phot.flux.perFreq
         phot.flux.perWave
         phot.flux.perEnergy
         phot.flux.perWavenumber
         phot.flux.perDecade                nu*F_nu, lambda*F_lambda,...

Looking at the current list, I'd also like to complain about

     phot.flux.sb

Since when is surface brightness a flux?   Surface brightness is an  
intensity and intensity != flux.  So...

     phot.intensity                                generic directed  
rate of radiant energy flow per unit area, time, and solid angle,  
surface brightness
     phot.intensity.bol                         (not generally  
needed, but here for symmetry)
     phot.intensity.perFreq
     phot.intensity.perWave
     phot.intensity.perEnergy
     phot.intensity.perWavenumber
     phot.intensity.perDecade            (Ibid.)

I know this is a bit of a change, but I frankly didn't notice  
before.... sorry!

Rick
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