Hi Lars,
Rspec is designed to be easy to use but has limited functionality.
BASS is the next level up. It has a lot more functionality and is a lot easier to use than say ISIS. ISIS is pretty much the gold standard in spectral processing, but is the hardest to use.
I suggest starting out with BASS as it is free, and see how you get on.
I also suggest starting simple. The A-type star is used to response correct the spectrum. This is to remove the bulk effect of the Earth’s atmosphere, and to adjust the bulk profile of the spectrum for the telescope and camera sensitivity. Note this doesn’t remove any spectral lines, just large scale features that affect the shape of the continuum. While this is important for getting a correct continuum, I wouldn’t bother with your first few spectra unless you really want to. I took spectra for 3 to 6 months before attempting a response correction.
When you are ready to do a response correction, then you will need to choose an A-type star at about the same altitude and on the night of your observation. The altitude of the star will affect the response correction as when you look lower down you are looking through more atmosphere. Also, atmospheric conditions can affect the response, so a response taken on one night may not work on another night.
Most important of all is to keep it fun! Don’t worry about getting things exactly right at the start.
Best wishes,
Andy