This 3.8° prism placed in front of your Star Analyser does improve resolution up to 130. Look at Christian Buil web page on Star Analyser for best use of this prism. This model is mounted on a ring for easier use with your Star Analyser.

            Designed for the advanced user looking for the maximum resolution, this device centralizes the spectrum on the optical axis and reduces the small amount of coma sometimes visible in the red region of spectra captured with the Star Analyser 100. 
            It is mounted in a 1.25" filter holder for direct attachment to the Star Analyser 100 and has been AR coated on both sides. 
            Alignment markings indicate correct orientation with the Star Analyser 100. It can be mounted either behind the SA100 (adding 15mm to the distance to the camera sensor) and held in place by an optional locking ring, or ahead of it. 
Note that with the prism in place, the wavelength scale becomes significantly non linear so a non linear wavelength calibration should be used.