Star Analyser 3.8° prism
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" threaded 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) or ahead of it. You can use some Teflon PTFE plumbers' tape or a small dab of Silicone bathtub caulk to lock its rotational orientation. The filter holder is also threaded to accept the optional lock ring that comes with the SA100.
Note that with the prism in place, the wavelength scale becomes significantly non-linear so a non-linear wavelength calibration should be used.