The maximum thickness of filter allowed is 12mm ; filters of thickness less than 3mm will require packing material to stop them moving about within the 3mm deep cut-out hole; filters of thickness 3-12 mm can be held in place with the standard filter masks and adjustable clamps.
It is important that the wheel is in balance, otherwise it might get
stuck when observing and moving the filter wheel at large zenith
distance. In the standard UBVRIZ or UBVRIH
setups, make sure
that the thick filters U, Z, and/or H
are mounted opposite to
each other.