use a gun cabinet /piano dehumifier !

I've been storing my reflector in a large plastic bag along with a couple of 8oz dessicant packs. This works fine if the scope is sealed while fairly dry and stored for long periods. Dessicant packs can only absorb a modest amount of moisture however and would need to be recharged (an hour in a low oven) occasionally.
A better solution would be the use of a commercial gun cabinet dehumidifier. There are several low power types available, a quick web search on 'gun cabinet dehumidifier' come up with several links, here's atypical one; http://www.kingmaker.net/mears0.htm
A device ike this is designed to prevent moisture problems with delicate and expensive items.
It's always interesting to discover that a product designed for a different niche market, like these dehumidifiers for pianos and gun cabinets, are ready made for the needs of the astro enthusiast.

As the son of a piano technician with over 30 years of experience I can honestly say that "dew chasers" as they are known for pianos are of more use chopped down and connected to a 12v power supply and used at night for dew prevention. They drive too much moisture out of pianos, which shinks the wooden parts and dries out various other components. In a high humidity environment they won't dry the air out enough and will lead to mold instead as the air becomes both hot and wet.

Joplin