I thought I would jump in with an example of how reddening affect can affect a spectrum. This is a spectrum of Brun 818. It is a B6 star behind the Orion nebula. It suffers from about 6.5 magnitudes of reddening in V, causing the slope of the spectrum in the optical to change direction!
To use such a star for response correction is tough. You either need a response corrected spectrum someone else has made, or you have to carefully deredden the spectrum.
If you have a good Miles spectrum that has not been dereddened, then this kind of scenario should be OK. Though with high reddening values you may end up with only a weak signal at the blue end.
On another topic that came up. When selecting the binning region for a spectrum, I stretch the image to make the full top and bottom edges of the spectrum visible. I then set the edge of the spectrum bin to include all of the signal, even the weak parts, while trying not to include any unnecessary background. I suspect this makes little difference, but if you set the binning region too narrow, then there is always a chance this will have a weird affect on the spectrum as you will be cutting out some of the signal.
Andy
