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Firstly, by dew control bands.. are you talking about a dew shield? or a heater band?
Also, which of your newt's mirrors is fogging? the primary or secondary?
For the secondary, a normal dew sheild should prevent dew for a certain amount of time depending on how damp the conditions are... you can buy secondary mirror heaters.. these are very effective...
Essentially, it should take some horrible conditions for dew to settle on your primary, as the long tube should act as a dew sheild... however a heater band wrapped around the tube right over where the primary mirror is housed should stave it off should that be fogging up...
The down side to heaters is that there will then be thermal currents inside your tube that will appear much like poor seeing through the eyepiece or camera...
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