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The pic is not very clear but I assume this is a newtonian? If so a dew heater strap is unnecessary. As` the primary is at the bottom of a solid tube it will almost never get dew on it and the heater will only act to induce image` degrading tube currents.
Normally a heater is only necessary on a scope if it has an exposed element such as a corrector plate on an SCT.
Things that do need dew control are eyepieces, finders, guidescopes if imaging and sometimes secondaries.
Malcolm
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