I'm using the SA-100 for low resolution spectroscopy. The achievable resolution is, among other factors, dependent on the grating to sensor distance. However, due to the limited back-focus capacity of my system (f/9.4) I could never get to the optimum distance that lies at 23 cm. In such a situation, the use of the SA-200 is recommended by Robin Leadbeater: http://www.threehill...optimum_spacing
I have now replaced the SA-100 by the SA-200 and the results look quite good:
The first test object was the quasi-stellar planetary nebula IC 2149 in Auriga:
10 Frames (300 sec. each) were stacked with Fitswork and analysed using RSpec. FWHM was determined for H beta and the results were compared (SA-100 vs. SA-200):
The resolution could be considerably improved using the SA-200. The [O III]-lines are now clearly resolved.
The second test object was Capella (alpha Aurigae). 50 Frames were stacked (250 msec each) and the spectrum was rectified. Using the SA-200 most of the famous Fraunhofer can be resolved:
A comparison with a spectrum of a G8 III standard star that was filtered to the approx. same resolution (Gaussian filter using VSpec) shows a good agreement:
In my situation the purchase of the SA-200 was a good decision. Its usage is, indeed, highly recommended if not enough back-focus is available.
However, there is still room for improvement: An excellent spectrum of Capella using the SA-100 (with better optics and a more experienced user) can be found here: