Any moist inside will effect the performance of the lenses and prisms. There are several methods to keep the optic dry on the inside.

Drying cartrigde (Trockenpatrone)

Two examples of wooden boxes which hold the cartridges in the transport case.

The bakelite container, the cartridge and the spanner to screw them in.

Two cartridges mounted in the head of a SR-9.

Refresh the internal climate.

With a special pump the optic could be given fresh dry air.

One of two “valves” to refresh the internal air of this 12 x 60. “Trockenluft” stands for dry air.

Small picture of the dry air pump.