[Prev][Next][Index][Thread]
(meteorobs) Re: meteorobs-digest V3 #147
I have seen several questions regarding dew on cameras/scopes in this list,
and I thought I'd send along a solution I came up with. I use the small
chemical handwarmer packets that are made for hunters and winter sports
enthusiasts. They require no electricity and produce no light or flame. They
do produce temperatures ranging from 123 - 146 deg F (51 to 63 deg C) over a
period of 7 to 10 hours. Most are based on the rapid oxidation of iron
powder upon exposure to air.
Simply activate one or more packets by opening and shaking it, and then
place them under your lens on a small, preferably insulated tray or
platform. The tray can be attached to your tripod, or suspended separately.
It helps to have sidewalls that direct the heat upward. If ambient light is
not a problem, you can line the insulated tray with mylar (from
metallic-looking party balloons) which reflects 80% of the heat directed at
it. In very calm conditions, you could probably get by with simply
suspending the packet from the lens on a string.
Occasionally, it helps to shake the packet again to expose more iron powder
to air and enhance the heat production. A packet or two in your pockets
feels good too!
They can be gotten through nearly any sporting goods or camping supply
store. I recently bought a 6-pack of packets on sale for $5 (US).
Fog-free lenses to all...
terry
To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html
References: