BC&F Telrad dew controller

Silly question # 100..................

Do dew control systems not cause heat convections (hot air waves) to travel upwards across the lens? thus causing shimmering.

Plugs into the standard dew controllers at 12V. I might just measure the resistance of it with my multimeter.......hold on........

150-170 ohms

Silly question # 100..................

Do dew control systems not cause heat convections (hot air waves) to travel upwards across the lens? thus causing shimmering.

True PJ, but on a zero magnification Telrad this is never an issue. Could be a problem on an objective / corrector it it is set too high. However dew tends to be a worse problem.

Thanks John. To be honest i dont even know what a Telrad is (ive just thought right now its a telescope radiator?). I imagine it to be a heated strip that fits around the lens to warm the air to stop dew building on it?

Now you say "zero magnification"...........i'm guessing it is a glass (or other material) heated shield that fits over the front of the scope.

I'll go and google it.

Ahhhhhhhhhhh ok. Now i see what it is. It fits over the EP? I would have thought the lens.

www.m33.org/0000D4CD-00858476.9/telrad1.jpg

Its amazing how fast that piece of glass fogs over, that heater pumps out about 1 watt of heat into the air, a dew heater or shield is practically essential for the telrad.

a dew heater or shield is practically essential for the telrad.

So a telrad is not a dew shield/heater?