The only sure way to know that you've got a supernova in your sights, especially shortly after an explosion, is to capture a diagnostic spectrum. Basically, supernovae come in two flavors: those that have hydrogen (Type II, from a very massive star that blows up) and those that don't (Type I, due to thermonuclear runaways in a less massive star).

Both types exhibit a wide variety of subclasses. Type Ia is of no interest because these stars don't emit neutrinos. Types Ib and Ic are thought to undergo core collapse like Type II supernovae and, therefore, should emit neutrinos.

As Maurice Gavin explains in "The Revival of Amateur Spectroscopy", low-resolution spectra of objects as faint as magnitude 13 or thereabouts are accessible to modest amateur equipment. (A few superposed 20-minute exposures with a 12-inch telescope or so should produce an adequate image.) But what will supernovae spectra look like — especially shortly after the outburst begins — as captured by small telescopes and low-resolution spectrographs?

Here's your field guide. To prepare it, we started with high-resolution, calibrated spectra supplied by Alexei Filippenko (University of California, Berkeley). Then, to simulate Gavin's CCD results, we degraded the spectra to a resolution of 50 angstroms per pixel. Finally, and with dramatic results, we changed the intensity along each spectrum to reflect variations in the unfiltered sensitivity of popular CCD chips — the KAF-0400 from Kodak and the ICX055BL from Sony. Thus, what you see here is what you will get! (Astrophotographers using panchromatic emulsions will record spectra that look much like the originals.)