Quote:
Originally Posted by mental4astro
For the primary mirror there is the typical heated strap option that is readily available from numerous suppliers, and I am working on another system too! See, full of surprises.
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Alex - you would never put active heat directly into a primary mirror via a heat strap to stop it from dewing up , it would ruin the optical figure . Refractors are more forgiving as they tend to be wrapped around the dew cap and lenses have 4 times the surface tolerance anyway .
Typical truss dobs even without shrouds tend to be a little warmer in the mirror box which helps with preventing dewing - a scope with a completely exposed mirror is always going to be tricky.