Vixen Collimating your R200SS - Manual (Page 3)

10.Again you need to adjust the position of the secondary mirror precisely with the
collimation screws “B”, “C” and “A”. When you shift the secondary mirror upper or
lower, turn the screws “B” or “C” only and don’t use the screw “A”. When you shift the
secondary mirror forward, turn the screw “A”. Turning the screws “A” and “B” evenly
shifts the secondary mirror backward.