That’s great !. If you still have problems with the spectrum horizontal, you can also adjust the ALPY grism to make the lines exactly vertical. If you look at the core module,you can see the grism held in place by allen head grub screws. If you loosen them off you can rotate the grism, viewing a spectrum by eye until the spectral lines are square to the dispersion direction. (Take care not to loosen to much and hold the grism holder in place as there is a spring behind it)
