  We use the progenitor of SN2012aw to illustrate the consequences of modeling
circumstellar dust using Galactic (interstellar) extinction laws that (1)
ignore dust emission in the near-IR and beyond; (2) average over dust
compositions, and (3) mis-characterize the optical/UV absorption by assuming
that scattered photons are lost to the observer. The primary consequences for
the progenitor of SN2012aw are that both the luminosity and the absorption are
significantly over-estimated. In particular, the stellar luminosity is most
likely in the range 10^4.8 < L/Lsun < 10^5.0 and the star was not extremely
massive for a Type IIP progenitor, with M < 15Msun. Given the properties of the
circumstellar dust and the early X-ray/radio detections of SN2012aw, the star
was probably obscured by an on-going wind with Mdot ~ 10^-5.5 to 10^-5.0
Msun/year at the time of the explosion, roughly consistent with the expected
mass loss rates for a star of its temperature (T_* ~ 3600K) and luminosity. In
the spirit of Galactic extinction laws, we supply simple interpolation formulas
for circumstellar extinction by dusty graphitic and silicate shells as a
function of wavelength (>0.3 micron) and total (absorption plus scattering)
V-band optical depth (tau < 20). These do not include the contributions of dust
emission, but provide a simple, physical alternative to incorrectly using
interstellar extinction laws.
