Measurement of the Spectrum of Supernova 2004etwith a DSS

Measurement of the Spectrum of Supernova 2004et
with a DSS-7 Spectrograph
Alan Holmes
10/9/2004

I recently measured the spectrum of Supernova 2004et with a DSS-7 Spectrograph and a Celestron C8-GPS. I had not successfully measured a supernova before and this one was relatively bright (magnitude 12.8) and well placed. Supernova 2004et is within the well known galaxy NGC6946. In Figure One below I show the DSS-7 entrance slit superimposed on the supernova (arrowed).

Figure 1

I collected five 15 minute exposures of the spectra and median combined them to yield the spectrum shown in Figure Two. The bright horizontal line superimposed on the sky background spectrum is the supernova. The C8 was guided with an STV and an E-finder.

Figure 2

The spectrum is shown below. The large hydrogen peak near 6500 angstroms is typical of type II supernovae. The sky background has been subtracted using SBIG’s SPECTRA program. The data has been corrected for spectrograph and CCD efficiency, but has not been smoothed so that the noise level can be seen.

Figure 3

I consider this result quite good for such a dim object. Supernova identification could be achieved on supernovae as faint as magnitude 15 with an 8 inch telescope. A 16 inch telescope could go 1.5 magnitudes further. This type of observation is one more example of the ability of the DSS-7 to reveal the information hidden within the spectrum of astronomical objects.