UBVRcIc filters

Though the UBVRI photometric system is classical in modern astronomy, UBVRcIc
filters are still fundamental for most of telescopes because of the past huge survey data.
Asahi has provided UBVRcIc filters which were made of the colored glass combination
suggested by Prof. Mike Bessell at RSAA in Australia.

However, it was not possible to produce large UBVRcIc filters due to the constraint of
colored glass size (max.165mm square) supplied by Schott.
It was also hard to get good transmitted wavefront due to epoxy glue which was used
to combine multi-substrates.

We succeeded in replacing the conventional colored glass based filters with all dielectric
coating design. The shape of passband is still similar to the conventional
UBVRclc filters, meanwhile the transmission is much higher, especially in U and B filter.
Thanks to monolithic substrate structure, image quality is also highly improved.

figure U, B, V, Rc, Ic filters