It seems that filter changes affect the focussing.
On this page we will collect empirical
focus offsets between filters. At
this stage it is best to determine these offsets during the day,
before the observations, but by collecting the information we may be
able to start predicting these.
Here are the offsets determined for the A -> B change, i.e. the changes required if the spectrograph was in focus with A and you change to B. negative values mean a counter-clockwise turn. From an unknown author.
L1 0.925 -> -0.45 L2 0.875 -> -0.40 L3 0.475 -> -0.00 R1 0.15 -> -0.725 R2 0.85 -> -0.425 R3 0.75 -> -0.32Here are the offsets for the AB -> B change, determined by KK/MM 2/4/2005
-0.5Last updated ND 28-03-2006